Android上在两个Activity之间传递Bitmap对象

Android上在两个Activity之间传递Bitmap对象
因为我做Android应用的时间不长，所以当我第一次在android之间传递Bitmap对象的时候我直接用了Intent.putExtra的方法实现了，当时我选择的是一张图像的ROI区域，所以工作的很好，但是当我尝试将整个图片做为Bitmap对象传到另外一个Activity中的时候总是得到一个错误fatal bind error我当时很郁闷了好久，后来google才发现是这样传递Bitmap对象的方式不对，Activity之间传递Bitmap有大小限制，而且这个大小限制很小，512x512的图片肯定会得到我上述的这个错误，于是我想到了先保存到SD卡上然后传递路径的方法，但是SD卡属于外部存储，可能不是特别方便，后来看到有人通过内部存储方式实现了在两个Activity之间传递Bitmap对象以及其它支持串行化的Java对象，我觉得很好，所以就写了这篇博客。关键点有如下：
1．  HTTP客户端下载图片，通过ImageView对象显示
2．  把ImageView上的Bitmap对象从当前Activity传递到另外一个
Activity中并显示出来
3．  基于串行化传递Java对象数据
 
首先看我是怎么实现HTTP客户端下载图片，通过异步Task接口实现HTTP客户端下载图片并通过Handler来更新ImageView，代码如下：
package com.example.sharedemo;

import java.io.IOException;
import java.io.InputStream;

import org.apache.http.HttpEntity;
import org.apache.http.HttpResponse;
import org.apache.http.HttpStatus;
import org.apache.http.client.ClientProtocolException;
import org.apache.http.client.HttpClient;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.impl.client.DefaultHttpClient;

import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.os.AsyncTask;
import android.os.Handler;
import android.os.Message;
import android.util.Log;

public class ImageLoadTask extends AsyncTask<String, Void, Bitmap> {
private Handler handler;

public ImageLoadTask(Handler handler) {
this.handler = handler;
}

protected void onPostExecute(Bitmap bitmap) {
Message msg = new Message();
msg.obj = bitmap;
handler.sendMessage(msg);
}

@Override
protected Bitmap doInBackground(String... urls) {
Bitmap bitmap = null;
// create HTTP client
HttpClient httpclient = new DefaultHttpClient();
try {
// GET request
Log.i("image-url", urls[0]);
HttpGet httpRequest = new HttpGet(urls[0]);
HttpResponse httpResponse = httpclient.execute(httpRequest);
if (httpResponse.getStatusLine().getStatusCode() == HttpStatus.SC_OK) {
// get entity from response
HttpEntity httpEntity = httpResponse.getEntity();
// read stream
InputStream is = httpEntity.getContent();
bitmap = BitmapFactory.decodeStream(is);
is.close();
Log.i("image", "already get the image by url : " + urls[0]);
}

} catch (ClientProtocolException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
} finally {
httpclient.getConnectionManager().shutdown();
}
return bitmap;
}

}
在当前的Activity中通过按钮上的事件响应实现切换View到对应的Activity中去，同时实现Java串行化数据传递。MainActivity的代码如下：
package com.example.sharedemo;

import java.io.ByteArrayOutputStream;
import java.io.FileOutputStream;

import android.app.Activity;
import android.content.Context;
import android.content.Intent;
import android.graphics.Bitmap;
import android.graphics.Matrix;
import android.graphics.drawable.BitmapDrawable;
import android.os.Bundle;
import android.os.Handler;
import android.os.Message;
import android.util.Log;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.ImageView;

public class MainActivity extends Activity implements OnClickListener{
public final static String SHARE_BITMAP_COMMAND = "share-image";
public final static String SHARE_TEXT_DATA_COMMAND = "share-text-data";
private Handler handler;

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

private void setupOnClickListener() {
Button bitmapBtn = (Button)this.findViewById(R.id.bitmapShareBtn);
bitmapBtn.setTag(SHARE_BITMAP_COMMAND);
bitmapBtn.setOnClickListener(this);
Button textDataBtn = (Button)this.findViewById(R.id.mapShareBtn);
textDataBtn.setTag(SHARE_TEXT_DATA_COMMAND);
textDataBtn.setOnClickListener(this);
final ImageView imageView = (ImageView)this.findViewById(R.id.imageView1);

handler = new Handler()
{
public void handleMessage(Message msg) {
Bitmap bitmap = (Bitmap)msg.obj;
if(bitmap != null)
{
/*
// 为防止原始图片过大导致内存溢出，这里先缩小原图显示，然后释放原始Bitmap占用的内存
Bitmap smallBitmap = zoomBitmap(bitmap, bitmap.getWidth()/ 5, bitmap.getHeight() / 5);
// 释放资源
bitmap.recycle();
// 显示图片
imageView.setImageBitmap(smallBitmap);
imageView.invalidate();
*/
imageView.setImageBitmap(bitmap);
}
}
};
ImageLoadTask task = new ImageLoadTask(handler);
task.execute("https://img-blog.csdn.net/20150607143208238");
}

public static Bitmap zoomBitmap(Bitmap bitmap, int width, int height) {
int w = bitmap.getWidth();
int h = bitmap.getHeight();
Matrix matrix = new Matrix();
float scaleWidth = ((float) width / w);
float scaleHeight = ((float) height / h);
matrix.postScale(scaleWidth, scaleHeight); // 不改变原来图像大小
Bitmap newbmp = Bitmap.createBitmap(bitmap, 0, 0, w, h, matrix, true);
return newbmp;
}

@Override
public void onClick(View v) {
Object tag = v.getTag();
Log.i("command", tag.toString());
if(SHARE_BITMAP_COMMAND.equals(tag))
{
Intent intent = new Intent(this.getApplicationContext(), ImageProcessActivity.class);
ImageView imageView = (ImageView)this.findViewById(R.id.imageView1);
Bitmap bitmap = ((BitmapDrawable)imageView.getDrawable()).getBitmap();
intent.putExtra("selectedImage", bitmap);
intent.putExtra("name", "lena");
intent.putExtra("description", "超级大美女");
this.startActivity(intent);
}
else if(SHARE_TEXT_DATA_COMMAND.equals(tag))
{
Intent intent = new Intent(this.getApplicationContext(), ImageProcessActivity.class);
ImageView imageView = (ImageView)this.findViewById(R.id.imageView1);
Bitmap bitmap = ((BitmapDrawable)imageView.getDrawable()).getBitmap();
// save it first then pass URI
ImageInfoBean dto = new ImageInfoBean();
String uri = createImageFromBitmap(bitmap);
dto.setDescription("超级大美女");
dto.setName("lena");
dto.setUri(uri);

intent.putExtra("tiger", dto);
this.startActivity(intent);
}
}

public String createImageFromBitmap(Bitmap bitmap) {
String fileName = "myImage";
try {
ByteArrayOutputStream bytes = new ByteArrayOutputStream();
bitmap.compress(Bitmap.CompressFormat.JPEG, 100, bytes);
FileOutputStream fo = openFileOutput(fileName, Context.MODE_PRIVATE);
fo.write(bytes.toByteArray());
fo.close();
} catch (Exception e) {
e.printStackTrace();
fileName = null;
}
Log.i("fileName", fileName);
return fileName;
}
}

对应另外一个Activity中实现读取与组装Bitmap对象显示的代码如下：
package com.example.sharedemo;

import java.io.FileNotFoundException;

import android.app.Activity;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.os.Bundle;
import android.widget.ImageView;
import android.widget.TextView;

public class ImageProcessActivity extends Activity {

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

private void backFillData() {
Object obj = this.getIntent().getExtras().get("tiger");
ImageView imageView = (ImageView)this.findViewById(R.id.imageView1);
TextView text1 = (TextView)this.findViewById(R.id.textView1);
TextView text2 = (TextView)this.findViewById(R.id.textView2);
try {
if(obj != null && obj instanceof ImageInfoBean)
{
ImageInfoBean dto = (ImageInfoBean)obj;
Bitmap bitmap = BitmapFactory.decodeStream(this.openFileInput(dto.getUri()));
imageView.setImageBitmap(bitmap);
imageView.invalidate(); // refresh

text1.setText("名称: " + dto.getName());
text2.setText("描述: " + dto.getDescription());
return;
}
} catch (FileNotFoundException e) {
e.printStackTrace();
}

Bitmap bitmap = (Bitmap) this.getIntent().getParcelableExtra("selectedImage");
String name = this.getIntent().getExtras().getString("name");
String description = this.getIntent().getExtras().getString("description");
if(bitmap != null)
{
imageView.setImageBitmap(bitmap);
imageView.invalidate(); // refresh
}
if(name != null)
{
text1.setText("名称: " + name);
}
if(description != null)
{
text2.setText("描述: " + description);
}
}

}
对应的Java串行化对象类代码如下：package com.example.sharedemo;

import java.io.Serializable;

public class ImageInfoBean implements Serializable {
/**
*
*/
private static final long serialVersionUID = 1L;

public String getName() {
return name;
}

public void setName(String name) {
this.name = name;
}

public String getDescription() {
return description;
}

public void setDescription(String description) {
this.description = description;
}

public String getUri() {
return uri;
}

public void setUri(String uri) {
this.uri = uri;
}

private String name;
private String description;
private String uri;

}
最后声明：别忘记在Manifest文件添加网络访问的权限
<uses-permission android:name="android.permission.INTERNET"/>


第一个按钮【传递图片】将会演示我遇到错误，第二按钮【传递文本数据】将会演示正确的处理结果，显示如下：