okHttp封装，使用超简单的网络请求实现

文章内容概要：

说明

实现

HttpUtil.getAsyn(url,param,new Callback() {
@Override
public void onFailure(Request request, IOException e) {
}
@Override
public void onResponse(final Response response) throws IOException {
}
});

HttpUtil.getAsyn(url,param,this);//this指的是Activity，必须实现Callback接口。

HttpUtil.getAsyn(url,param);//不关心返回时调用。

//BaseActivity部分代码
public abstract class BaseActivity extends Activity {
public static final String TAG = BaseActivity.class.getSimpleName();
protected Handler mHandler = null;
public BaseUtil baseUtil;
public HttpUtil httpUtil;
@Override
protected void onCreate(Bundle savedInstanceState) {
// TODO Auto-generated method stub
super.onCreate(savedInstanceState);
baseUtil = new BaseUtil(this);
//初始化httpUtil，并将this引用作为参数
httpUtil = new HttpUtil(this);
//初始化mHandler，用于子线程向主线程发消息
initHandler();
}
//实现了一个http请求返回调用的空方法
protected void httpResponse(String url, Map<String, Object> params, Object result) {

}
//文件下载完成后回调，空方法
protected void completeDownload(String abstractPath) {
}

////请求出错回调，默认提示网络请求失败
void httpError(String url, Map<String, Object> params) {
mHandler.post(new Runnable() {

@Override
public void run() {
Toast.makeText(BaseActivity.this, "网络请求失败", 300).show();
}
});
}
.
.
.
}

//HttpUtil部分代码，这里也并非面对真正的okHttp封装，而在之上又包了一层。
//边写边想的时候发现这一层如果拿掉也不是不可以，但这样至少我们直接面对的代码是比较简洁的。
public class HttpUtil {
private BaseActivity activity;
public HttpUtil(BaseActivity activity) {
this.activity = activity;
}
public Map<String, Object> getSyncHttp(String url) {
try {
Response response = OkHttpEngine.getInstance().getSyncHttp(activity, url);
Map<String, Object> result = new HashMap<>();
return result;
} catch (IOException e) {
return null;
}
}
.
.
.
}

public void httpTest(){
this.httpUtil.getAsynHttp("https://www.baidu.com", p1);
ImageView view = findView(R.id.imageview);
// 加载图片
this.httpUtil.displayImage(mHandler, view, "https://www.baidu.com/img/bd_logo1.png", R.drawable.no_image);
String p = MyApplication.mkdirs("/net_image/a/b");
//下载文件保存到sdcard/net_image/a/b文件夹下。
this.httpUtil.downloadFile("http://a4.att.hudong.com/23/09/01300000165488122547095974400.jpg", p);
}

BaseActivity.java

package com.mydemo.common;

import java.util.Map;

import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.os.Handler;
import android.view.View;
import android.widget.Toast;

public abstract class BaseActivity extends Activity {

public static final String TAG = BaseActivity.class.getSimpleName();

protected Handler mHandler = null;

public BaseUtil baseUtil;

public HttpUtil httpUtil;

@Override
protected void onCreate(Bundle savedInstanceState) {
// TODO Auto-generated method stub
super.onCreate(savedInstanceState);
baseUtil = new BaseUtil(this);
httpUtil = new HttpUtil(this);
initHandler();
}

protected void initHandler() {
mHandler = new Handler();
}

public <T> T findView(int id) {

View view = findViewById(id);
if (view == null || view.toString().equals("")) {
return null;
}
return (T) view;
}

/**
* 通过类名启动Activity
*
* @param pClass
*/
protected void openActivity(Class<?> pClass) {
openActivity(pClass, null);
}

/**
* 通过类名启动Activity，并且含有Bundle数据
*
* @param pClass
* @param pBundle
*/
protected void openActivity(Class<?> pClass, Bundle pBundle) {
Intent intent = new Intent(this, pClass);
if (pBundle != null) {
intent.putExtras(pBundle);
}
startActivity(intent);
}

/**
* 通过Action启动Activity
*
* @param pAction
*/
protected void openActivity(String pAction) {
openActivity(pAction, null);
}

/**
* 通过Action启动Activity，并且含有Bundle数据
*
* @param pAction
* @param pBundle
*/
protected void openActivity(String pAction, Bundle pBundle) {
Intent intent = new Intent(pAction);
if (pBundle != null) {
intent.putExtras(pBundle);
}
startActivity(intent);
}

protected void httpResponse(String url, Map<String, Object> params, Object result) {

}

protected void completeDownload(String abstractPath) {
}

protected void httpError(String url, Map<String, Object> params, final Exception e) {
mHandler.post(new Runnable() {

@Override
public void run() {
Toast.makeText(BaseActivity.this, "网络请求失败:" + e.getMessage(), 4000).show();
}
});
}

void httpError(String url, Map<String, Object> params) {
mHandler.post(new Runnable() {

@Override
public void run() {
Toast.makeText(BaseActivity.this, "网络请求失败", 300).show();
}
});
}

}

[b]BaseUtil

package com.mydemo.common;

import java.util.Locale;

import android.content.Context;
import android.content.pm.PackageInfo;
import android.content.pm.PackageManager;
import android.telephony.TelephonyManager;
import android.view.inputmethod.InputMethodManager;
import android.widget.EditText;
import android.widget.Toast;

public class BaseUtil {
private Context context;

protected InputMethodManager imm;

private TelephonyManager tManager;

public BaseUtil(Context context) {
this.context = context;
tManager = (TelephonyManager) context.getSystemService(context.TELEPHONY_SERVICE);
imm = (InputMethodManager) context.getSystemService(context.INPUT_METHOD_SERVICE);
}

public void DisPlay(String content) {
Toast.makeText(context, content, 1).show();
}

public void DisplayToast(String str) {
Toast.makeText(context, str, Toast.LENGTH_SHORT).show();
}

public void hideOrShowSoftInput(boolean isShowSoft, EditText editText) {
if (isShowSoft) {
imm.showSoftInput(editText, 0);
} else {
imm.hideSoftInputFromWindow(editText.getWindowToken(), 0);
}
}

// 获得当前程序版本信息
public String getVersionName() throws Exception {
// 获取packagemanager的实例
PackageManager packageManager = context.getPackageManager();
// getPackageName()是你当前类的包名，0代表是获取版本信息
PackageInfo packInfo = packageManager.getPackageInfo(context.getPackageName(), 0);
return packInfo.versionName;
}

// 獲得設備信息
public String getDeviceId() throws Exception {
String deviceId = tManager.getDeviceId();

return deviceId;
}

/**
* 获取SIM卡序列号
*
* @return
*/
public String getToken() {
return tManager.getSimSerialNumber();
}

/* 獲得系統版本 */

public String getClientOs() {
return android.os.Build.ID;
}

/* 獲得系統版本號 */
public String getClientOsVer() {
return android.os.Build.VERSION.RELEASE;
}

// 獲得系統語言包
public String getLanguage() {
return Locale.getDefault().getLanguage();
}

public String getCountry() {

return Locale.getDefault().getCountry();
}

}

HttpUtil

package com.mydemo.common;

import java.io.File;
import java.io.IOException;
import java.util.HashMap;
import java.util.Map;

import android.os.Handler;
import android.widget.ImageView;

import com.squareup.okhttp.Response;

public class HttpUtil {

private BaseActivity activity;

public HttpUtil(BaseActivity activity) {
this.activity = activity;
}

public void getAsynHttp(String url, Map<String, Object> params) {
OkHttpEngine.getInstance().getAsynHttp(activity, url);
}

public Map<String, Object> getSyncHttp(String url) {
try {
Response response = OkHttpEngine.getInstance().getSyncHttp(activity, url);
Map<String, Object> result = new HashMap<>();
return result;
} catch (IOException e) {
return null;
}
}

public void post(String url, Map<String, Object> params) {
OkHttpEngine.getInstance().postAsynHttp(activity, url, params);
}

public void downloadFile(final String url, final String destFileDir) {
OkHttpEngine.getInstance().downloadFile(activity, url, destFileDir);
}

public void displayImage(final Handler mHandler, final ImageView view, final String imgUrl, final int errorResId) {
OkHttpEngine.getInstance().displayImage(mHandler, view, imgUrl, errorResId);
}

public void fileUpload(final String url, final Map<String, Object> params, File[] files, String[] fileKeys) {
OkHttpEngine.getInstance().fileUpload(activity, url, params, files, fileKeys);
}

}

ImageUtil

package com.mydemo.common;

import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.InputStream;
import java.lang.reflect.Field;

import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.util.DisplayMetrics;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ImageView;

/**
*/
public class ImageUtils {
/**
* 根据InputStream获取图片实际的宽度和高度
*/
public static ImageSize getImageSize(InputStream imageStream) {
BitmapFactory.Options options = new BitmapFactory.Options();
options.inJustDecodeBounds = true;
BitmapFactory.decodeStream(imageStream, null, options);
return new ImageSize(options.outWidth, options.outHeight);
}

public static class ImageSize {
int width;

int height;

public ImageSize() {
}

public ImageSize(int width, int height) {
this.width = width;
this.height = height;
}

@Override
public String toString() {
return "ImageSize{" + "width=" + width + ", height=" + height + '}';
}
}

public static int calculateInSampleSize(ImageSize srcSize, ImageSize targetSize) {
// 源图片的宽度
int width = srcSize.width;
int height = srcSize.height;
int inSampleSize = 1;

int reqWidth = targetSize.width;
int reqHeight = targetSize.height;

if (width > reqWidth && height > reqHeight) {
// 计算出实际宽度和目标宽度的比率
int widthRatio = Math.round((float) width / (float) reqWidth);
int heightRatio = Math.round((float) height / (float) reqHeight);
inSampleSize = Math.max(widthRatio, heightRatio);
}
return inSampleSize;
}

/**
* 根据ImageView获适当的压缩的宽和高
*/
public static ImageSize getImageViewSize(View view) {

ImageSize imageSize = new ImageSize();

imageSize.width = getExpectWidth(view);
imageSize.height = getExpectHeight(view);

return imageSize;
}

/**
* 根据view获得期望的高度
*/
private static int getExpectHeight(View view) {

int height = 0;
if (view == null) return 0;

final ViewGroup.LayoutParams params = view.getLayoutParams();
// 如果是WRAP_CONTENT，此时图片还没加载，getWidth根本无效
if (params != null && params.height != ViewGroup.LayoutParams.WRAP_CONTENT) {
height = view.getWidth(); // 获得实际的宽度
}
if (height <= 0 && params != null) {
height = params.height; // 获得布局文件中的声明的宽度
}

if (height <= 0) {
height = getImageViewFieldValue(view, "mMaxHeight");// 获得设置的最大的宽度
}

// 如果宽度还是没有获取到，憋大招，使用屏幕的宽度
if (height <= 0) {
DisplayMetrics displayMetrics = view.getContext().getResources().getDisplayMetrics();
height = displayMetrics.heightPixels;
}

return height;
}

/**
* 根据view获得期望的宽度
*/
private static int getExpectWidth(View view) {
int width = 0;
if (view == null) return 0;

final ViewGroup.LayoutParams params = view.getLayoutParams();
// 如果是WRAP_CONTENT，此时图片还没加载，getWidth根本无效
if (params != null && params.width != ViewGroup.LayoutParams.WRAP_CONTENT) {
width = view.getWidth(); // 获得实际的宽度
}
if (width <= 0 && params != null) {
width = params.width; // 获得布局文件中的声明的宽度
}

if (width <= 0)

{
width = getImageViewFieldValue(view, "mMaxWidth");// 获得设置的最大的宽度
}
// 如果宽度还是没有获取到，憋大招，使用屏幕的宽度
if (width <= 0)

{
DisplayMetrics displayMetrics = view.getContext().getResources().getDisplayMetrics();
width = displayMetrics.widthPixels;
}

return width;
}

/**
* 通过反射获取imageview的某个属性值
*/
private static int getImageViewFieldValue(Object object, String fieldName) {
int value = 0;
try {
Field field = ImageView.class.getDeclaredField(fieldName);
field.setAccessible(true);
int fieldValue = field.getInt(object);
if (fieldValue > 0 && fieldValue < Integer.MAX_VALUE) {
value = fieldValue;
}
} catch (Exception e) {
}
return value;

}

public static Bitmap getLoacalBitmap(String url) {
try {
FileInputStream fis = new FileInputStream(url);
return BitmapFactory.decodeStream(fis);
} catch (FileNotFoundException e) {
e.printStackTrace();
return null;
}
}
}

okHttp封装

package com.mydemo.common;

import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.net.FileNameMap;
import java.net.URLConnection;
import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;
import java.util.Map.Entry;
import java.util.Set;
import java.util.concurrent.TimeUnit;

import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.os.Handler;
import android.widget.ImageView;

import com.squareup.okhttp.Cache;
import com.squareup.okhttp.Call;
import com.squareup.okhttp.Callback;
import com.squareup.okhttp.FormEncodingBuilder;
import com.squareup.okhttp.Headers;
import com.squareup.okhttp.MediaType;
import com.squareup.okhttp.MultipartBuilder;
import com.squareup.okhttp.OkHttpClient;
import com.squareup.okhttp.Request;
import com.squareup.okhttp.RequestBody;
import com.squareup.okhttp.Response;

public class OkHttpEngine {

private static OkHttpEngine okHttpEngine;

private OkHttpClient mOkHttpClient;

public static synchronized void initEngine() {
okHttpEngine = new OkHttpEngine();
}

public static OkHttpEngine getInstance() {
if (okHttpEngine == null) {
initEngine();
}
return okHttpEngine;
}

private OkHttpEngine() {
mOkHttpClient = new OkHttpClient();
mOkHttpClient.setConnectTimeout(15, TimeUnit.SECONDS);
mOkHttpClient.setWriteTimeout(20, TimeUnit.SECONDS);
mOkHttpClient.setReadTimeout(20, TimeUnit.SECONDS);
}

public OkHttpEngine setCache(Context mContext) {
File sdcache = mContext.getExternalCacheDir();
int cacheSize = 10 * 1024 * 1024;
mOkHttpClient.setCache(new Cache(sdcache.getAbsoluteFile(), cacheSize));
return okHttpEngine;
}

/**
* @param currentActivity
*            当前活动的activity对象
* @param url
*            请求地址
* @param params
*            参数
*/
public void getAsynHttp(final BaseActivity currentActivity, final String url) {

final Request request = new Request.Builder().url(url).build();
Call call = mOkHttpClient.newCall(request);
call.enqueue(new Callback() {
@Override
public void onFailure(Request request, IOException e) {
}

@Override
public void onResponse(final Response response) throws IOException {
String str = response.body().string();
currentActivity.httpResponse(url, null, str);
}
});
}

public Response getSyncHttp(final BaseActivity currentActivity, final String url) throws IOException {
// OkHttpClient mOkHttpClient = new OkHttpClient();
final Request request = new Request.Builder().url(url).build();
Call call = mOkHttpClient.newCall(request);
Response mResponse = call.execute();
if (mResponse.isSuccessful()) {
currentActivity.httpResponse(url, null, mResponse.body().string());
return mResponse;
} else {
currentActivity.httpError(url, null);
}
return null;
}

public void postAsynHttp(final BaseActivity currentActivity, final String url, final Map<String, Object> params) {
// OkHttpClient mOkHttpClient = new OkHttpClient();
FormEncodingBuilder builer = _getFormBuilder(params);
Request request = new Request.Builder().url(url).post(builer.build()).build();
Call call = mOkHttpClient.newCall(request);
call.enqueue(new Callback() {
@Override
public void onFailure(Request request, IOException e) {
currentActivity.httpError(url, params);
}

@Override
public void onResponse(Response response) throws IOException {
currentActivity.httpResponse(url, params, response.body().string());
}
});
}

public void fileUpload(final BaseActivity currentActivity, final String url, final Map<String, Object> params, File[] files, String[] fileKeys) {

Request request = buildMultipartFormRequest(url, files, fileKeys, params);

Call call = mOkHttpClient.newCall(request);
call.enqueue(new Callback() {
@Override
public void onFailure(Request request, IOException e) {
currentActivity.httpError(url, params);
}

@Override
public void onResponse(Response response) throws IOException {
String str = response.body().string();
currentActivity.httpResponse(url, params, response.body().string());
}
});
}

/**
* 下载文件，返回文件绝对路径
*
* @param currentActivity
* @param url
*            文件网络地址
* @param destFileDir
*            文件存储位置
*/
public void downloadFile(final BaseActivity currentActivity, final String url, final String destFileDir) {
final Request request = new Request.Builder().url(url).build();
final Call call = mOkHttpClient.newCall(request);
call.enqueue(new Callback() {
@Override
public void onFailure(final Request request, final IOException e) {
currentActivity.httpError(url, new HashMap<String, Object>());
}

@Override
public void onResponse(Response response) {
InputStream is = null;
byte[] buf = new byte[2048];
int len = 0;
FileOutputStream fos = null;
try {
is = response.body().byteStream();
File file = new File(destFileDir, getFileName(url));
fos = new FileOutputStream(file);
while ((len = is.read(buf)) != -1) {
fos.write(buf, 0, len);
}
fos.flush();
Map<String, Object> params = new HashMap<String, Object>();
currentActivity.completeDownload(file.getAbsolutePath());
} catch (IOException e) {
e.printStackTrace();
currentActivity.httpError(url, new HashMap<String, Object>(), e);
} finally {
try {
if (is != null)
is.close();
} catch (IOException e) {
}
try {
if (fos != null)
fos.close();
} catch (IOException e) {
}
}

}
});
}

public void displayImage(final Handler mHandler, final ImageView view, final String imgUrl, final int errorResId) {
final Request request = new Request.Builder().url(imgUrl).build();
Call call = mOkHttpClient.newCall(request);
call.enqueue(new Callback() {
@Override
public void onFailure(Request request, IOException e) {
mHandler.post(new Runnable() {
@Override
public void run() {
view.setImageResource(errorResId);
}
});
}

@Override
public void onResponse(Response response) {
InputStream is = null;
try {
is = response.body().byteStream();
ImageUtils.ImageSize actualImageSize = ImageUtils.getImageSize(is);
ImageUtils.ImageSize imageViewSize = ImageUtils.getImageViewSize(view);
int inSampleSize = ImageUtils.calculateInSampleSize(actualImageSize, imageViewSize);
try {
is.reset();
} catch (IOException e) {
response = _getAsyn(imgUrl);
is = response.body().byteStream();
}

BitmapFactory.Options ops = new BitmapFactory.Options();
ops.inJustDecodeBounds = false;
ops.inSampleSize = inSampleSize;
final Bitmap bm = BitmapFactory.decodeStream(is, null, ops);
mHandler.post(new Runnable() {
@Override
public void run() {
view.setImageBitmap(bm);
}
});
} catch (Exception e) {
setErrorResId(mHandler, view, errorResId);

} finally {
if (is != null)
try {
is.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
});

}

/**
* 同步的Get请求
*
* @param url
* @return Response
*/
private Response _getAsyn(String url) throws IOException {
final Request request = new Request.Builder().url(url).build();
Call call = mOkHttpClient.newCall(request);
Response execute = call.execute();
return execute;
}

private FormEncodingBuilder _getFormBuilder(Map<String, Object> params) {
FormEncodingBuilder builder = new FormEncodingBuilder();
if (params != null && params.size() > 0) {
Set<Entry<String, Object>> set = params.entrySet();
Iterator<Entry<String, Object>> iterator = set.iterator();
while (iterator.hasNext()) {
Entry<String, Object> entry = iterator.next();
builder.add(entry.getKey(), entry.getValue().toString());
}
}
return builder;
}

private Request buildMultipartFormRequest(String url, File[] files, String[] fileKeys, final Map<String, Object> params) {

MultipartBuilder builder = new MultipartBuilder().type(MultipartBuilder.FORM);

if (params != null && params.size() > 0) {
Set<Entry<String, Object>> set = params.entrySet();
Iterator<Entry<String, Object>> iterator = set.iterator();
while (iterator.hasNext()) {
Entry<String, Object> entry = iterator.next();
builder.addPart(Headers.of(String.format("Content-Disposition", "form-data; name=\"%s\"", entry.getKey())), RequestBody.create(null, entry.getValue().toString()));
}
}

if (files != null) {
RequestBody fileBody = null;
for (int i = 0; i < files.length; i++) {
File file = files[i];
String fileName = file.getName();
fileBody = RequestBody.create(MediaType.parse(guessMimeType(fileName)), file);
// TODO 根据文件名设置contentType
builder.addPart(Headers.of("Content-Disposition", "form-data; name=\"" + fileKeys[i] + "\"; filename=\"" + fileName + "\""), fileBody);
}
}

RequestBody requestBody = builder.build();
return new Request.Builder().url(url).post(requestBody).build();
}

private String guessMimeType(String path) {
FileNameMap fileNameMap = URLConnection.getFileNameMap();
String contentTypeFor = fileNameMap.getContentTypeFor(path);
if (contentTypeFor == null) {
contentTypeFor = "application/octet-stream";
}
return contentTypeFor;
}

private String getFileName(String path) {
int separatorIndex = path.lastIndexOf("/");
return (separatorIndex < 0) ? path : path.substring(separatorIndex + 1, path.length());
}

private void setErrorResId(final Handler mHandler, final ImageView view, final int errorResId) {
mHandler.post(new Runnable() {
@Override
public void run() {
view.setImageResource(errorResId);
}
});
}
}

MainActivity

package com.mydemo.ui;

import java.util.HashMap;
import java.util.Map;

import com.mydemo.MyApplication;
import com.mydemo.common.BaseActivity;
import com.mydemo.common.ImageUtils;
import com.mydemo.okhttp.R;

import android.os.Bundle;
import android.os.Handler;
import android.os.Message;
import android.widget.ImageView;
import android.widget.TextView;

public class MainActivity extends BaseActivity {

private final String BAIDU_INDEX1 = "http://www.baidu.com";

@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);

mHandler = new Handler(getMainLooper()) {

@Override
public void handleMessage(Message msg) {
super.handleMessage(msg);
switch (msg.what) {
case 1:
break;
}
}
};
Map<String, Object> p1 = new HashMap<String, Object>();
this.httpUtil.getAsynHttp(BAIDU_INDEX1, p1);

// this.getAsynHttp(BAIDU_INDEX2, p1);
//
// this.getAsynHttp(BAIDU_INDEX3, p1);
// 要调用同步GET方法，但需要另起一个子线程发起请求，而不能直接在主线程发起请求。
/*
* Thread t = new Thread(new Runnable() {
* @Override
* public void run() {
* Map<String, Object> p1 = new HashMap<>();
* p1.put("s", System.currentTimeMillis());
* MainActivity.this.getSyncHttp(BAIDU_INDEX4, p1);
* }
* });
* t.start();
*/
this.httpUtil.getAsynHttp(BAIDU_INDEX1, p1);
ImageView view = findView(R.id.imageview);
// 加载图片
this.httpUtil.displayImage(mHandler, view, "https://www.baidu.com/img/bd_logo1.png", R.drawable.no_image);
String p = MyApplication.mkdirs("/net_image/a/b");
this.httpUtil.downloadFile("http://a4.att.hudong.com/23/09/01300000165488122547095974400.jpg", p);
}

@Override
public void httpResponse(String url, Map<String, Object> params, Object result) {
Message msg = new Message();
switch (url) {
case BAIDU_INDEX1:
msg.what = 1;
msg.obj = result;
mHandler.sendMessage(msg);
break;
}

}

@Override
public void completeDownload(final String abstractPath) {
super.completeDownload(abstractPath);
mHandler.post(new Runnable() {
@Override
public void run() {
ImageView view5 = findView(R.id.imageview2);
view5.setImageBitmap(ImageUtils.getLoacalBitmap(abstractPath));
TextView view1 = findView(R.id.result5);
view1.setText("存储位置:" + abstractPath);
}
});
}

@Override
protected void httpError(String url, Map<String, Object> params, final Exception e) {
mHandler.post(new Runnable() {

@Override
public void run() {
TextView view4 = findView(R.id.result5);
view4.setText(e.getMessage());
}
});
}

}

Application

package com.mydemo;

import java.io.File;

import android.app.Application;
import android.os.Environment;

public class MyApplication extends Application {

static MyApplication application = new MyApplication();

@Override
public void onCreate() {
super.onCreate();
}

private MyApplication() {

}

public static MyApplication getApplication() {
return application;
}

public static String getSDPath() {
File sdDir = null;
boolean sdCardExist = Environment.getExternalStorageState().equals(android.os.Environment.MEDIA_MOUNTED);// 判断sd卡是否存在
if (sdCardExist) {
sdDir = Environment.getExternalStorageDirectory();// 获取跟目录
}
return sdDir.toString();
}

public static String mkdirs(String path) {
String sdcard = getSDPath();
if (path.indexOf(getSDPath()) == -1) {
path = sdcard + (path.indexOf("/") == 0 ? "" : "/") + path;
}
File destDir = new File(path);
if (!destDir.exists()) {
path = createDir(path);
if (path == null) {
return null;
}
}
return path;
}

//不限层级创建文件夹，
private static String createDir(String path) {
String sdPath = getSDPath();
String[] dirs = path.replace(sdPath, "").split("/");
StringBuffer filePath = new StringBuffer(sdPath);
for (String dir : dirs) {
if (!"".equals(dir) && !dir.equals(sdPath)) {
filePath.append("/").append(dir);
File destDir = new File(filePath.toString());
if (!destDir.exists()) {
boolean b = destDir.mkdirs();
if (!b) {
return null;
}
}
}
}
return filePath.toString();
}
}

activity_main.xml

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:layout_marginLeft="20dp"
android:orientation="vertical" >

<TextView
android:id="@+id/result1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginTop="10dp"
android:text="@string/hello_world" />

<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginTop="10dp"
android:text="百度图片是直接显示的网络图片" />

<ImageView
android:id="@+id/imageview"
android:layout_width="200dp"
android:layout_height="200dp"
android:layout_gravity="center_horizontal"
android:layout_marginTop="5dp"
android:contentDescription="网络图片" />

<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginTop="5dp"
android:text="下面这张图是下载在本地后，再加载显示的" />

<TextView
android:id="@+id/result5"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginTop="10dp"
android:text="@string/hello_world" />

<ImageView
android:id="@+id/imageview2"
android:layout_width="300dp"
android:layout_height="300dp"
android:layout_gravity="center_horizontal"
android:layout_marginTop="5dp"
android:contentDescription="网络图片" />

</LinearLayout>