从相册选取照片

明确：

Android 从4.4(API19)版本开始选取相册中的图片不再时返回真实图片的Uri，而是封装过的Uri，因此如果是4.4版本以上的手机需要对这个uri进行解析。4.4以下的版本不需要，因为返回的是真实的uri

判断Uri是document类型的话，需要取出docume id进行处理 ，如果是media类型的话还需要进一步解析

package com.example.choosepictest;

import android.content.ContentUris;
import android.content.Intent;
import android.database.Cursor;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.net.Uri;
import android.os.Build;
import android.os.Environment;
import android.provider.DocumentsContract;
import android.provider.MediaStore;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.ImageButton;
import android.widget.ImageView;
import android.widget.Toast;

import java.io.File;
import java.io.FileNotFoundException;
import java.io.IOException;

public class MainActivity extends AppCompatActivity {

public static  final  int TAKE_PHOTO = 1;

public  static final int CROP_PHOTO = 2 ;

public  static  final  int CHOOSE_PHOTO = 3;

private Button chooseFromAlbum ;

private Button takephoto;

private ImageView picture ;

private Uri imageUri ;

@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
takephoto = (Button) findViewById(R.id.take_phone);
picture = (ImageView) findViewById( R.id.picture) ;
chooseFromAlbum = (Button) findViewById(R.id.choose_from_album);
takephoto.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
//创建File对象，用于存储拍照后的照片
File outputImage = new File(Environment.getExternalStorageDirectory(),"output_image.jpg");
System.out.println(Environment.getExternalStorageDirectory());
try {
if(outputImage.exists()){
outputImage.delete();
}
outputImage.createNewFile();
}catch (IOException e){
e.printStackTrace();
}
imageUri = Uri.fromFile(outputImage);
Intent intent = new Intent("android.media.action.IMAGE_CAPTURE");
intent.putExtra(MediaStore.EXTRA_OUTPUT,imageUri);
startActivityForResult(intent , TAKE_PHOTO);//需要返回结果判断拍照成功的故用这个方法
}
});

chooseFromAlbum.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
Intent intent = new Intent("android.intent.action.GET_CONTENT");
intent.setType("image/*");
startActivityForResult(intent , CHOOSE_PHOTO);
}
});

}

@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
switch (requestCode){
case TAKE_PHOTO:
if(resultCode == RESULT_OK){
Intent intent = new Intent("com.android.camera.action.CROP");//为系统剪裁的Action

intent.setDataAndType(imageUri ,"image/*"); //设置剪裁的属性类型
intent.putExtra("scale",true);//scale为缩放的意思

intent.putExtra(MediaStore.EXTRA_OUTPUT , imageUri);
startActivityForResult(intent , CROP_PHOTO); //需要返回结果来判断是否截图成功的故用这个方法

}
break;
case CROP_PHOTO:
if(resultCode==RESULT_OK){
try{

Bitmap bitmap = BitmapFactory.decodeStream(getContentResolver().openInputStream(imageUri));//而contentresolver则是用于管理所有程序的contentprovider实例
picture.setImageBitmap(bitmap);
}catch (FileNotFoundException e){
e.printStackTrace();
}
}
break;
case CHOOSE_PHOTO:
if(resultCode == RESULT_OK){
if(Build.VERSION.SDK_INT>=19){
//4.4及以上系统使用
handleImageOnKitKat(data);
}else{
handleImageBeforeKitKat(data);
}
}
break;
default:break;
}
}

private void handleImageOnKitKat(Intent data){
String imagePath = null ;
Uri uri = data.getData();
//        if(DocumentsContract.isDocumentUri(this , uri))
4000
{
//            //如果是Document类型的Uri，则通过document id 处理
//            String docId = DocumentsContract.getDocumentId(uri);
//            if("com.android.providers.media.document".equals(uri.getAuthority())){
//                String id = docId.split(":")[1];//解析出数字格式id字符串分割
//                String selection = MediaStore.Images.Media._ID+"=" + id;
//                imagePath = getImagePath(MediaStore.Images.Media.EXTERNAL_CONTENT_URI , selection);
//            }else if("com.android.providers.downloads.documents".equals(uri.getAuthority())){
//                Uri contentUri = ContentUris.withAppendedId(Uri.parse("content://downloads/public_downloads"),Long.valueOf(docId));
//                imagePath = getImagePath(contentUri,null);
//            }
//
//        }else if("content".equalsIgnoreCase(uri.getScheme())){
//            //如果不是document类型的Uri，则用普通方式处理
//            imagePath = getImagePath(uri , null);
//
//        }
//
//        disPlayImage(imagePath);
}

private void handleImageBeforeKitKat(Intent data){
Uri uri = data.getData() ;//获取图片真实的uri
//  System.out.println(uri);
String imagePath = getImagePath(uri , null);
disPlayImage(imagePath);
}

private String getImagePath(Uri uri , String selection){
String path = null ;
//通过uri和selection来获取真实的图片路径
Cursor cursor = getContentResolver().query(uri , null , selection ,null , null);
if(cursor !=null){
if (cursor.moveToNext()){
path = cursor.getString(cursor.getColumnIndex(MediaStore.Images.Media.DATA));
}
cursor.close();
}
return path ;
}

private  void disPlayImage(String imagePath){
if (imagePath!=null){
Bitmap bitmap = BitmapFactory.decodeFile(imagePath);
picture.setImageBitmap(bitmap);
}else {
Toast.makeText(this , "failed to get image",Toast.LENGTH_SHORT).show();
}
}
}

<?xml version="1.0" encoding="utf-8"?>
<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:orientation="vertical"
>
<Button
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="Take photo"
android:id="@+id/take_phone"/>
<Button
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:id="@+id/choose_from_album"
android:text="Choose From Album" />
<ImageView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:id="@+id/picture"
android:layout_gravity="center_vertical"/>
</LinearLayout>

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.example.choosepictest">
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>
<application
android:allowBackup="true"
android:icon="@mipmap/ic_launcher"
android:label="@string/app_name"
android:supportsRtl="true"
android:theme="@style/AppTheme">
<activity android:name=".MainActivity">
<intent-filter>
<action android:name="android.intent.action.MAIN" />

<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
</application>

</manifest>