从相册打开照片

折腾了三个多小时，程序无Bug，但是就是打不开照片。。。
完全照着郭老师的代码敲得。。。
版本不一样，想打开郭老师源代码，居然失败。。。
还需要进一步折腾，
吃点饭，
回来继续。
=============================
把郭老师的代码粘过来，果然能用。。。
实在找不到不一样的地方，先放放吧，将来会调试了在研究。
郭老师代码：
  1 package com.example.cameraalbumtest;
  2 
  3 import android.Manifest;
  4 import android.annotation.TargetApi;
  5 import android.content.ContentUris;
  6 import android.content.Intent;
  7 import android.content.pm.PackageManager;
  8 import android.database.Cursor;
  9 import android.graphics.Bitmap;
 10 import android.graphics.BitmapFactory;
 11 import android.net.Uri;
 12 import android.os.Build;
 13 import android.os.Bundle;
 14 import android.os.Environment;
 15 import android.provider.DocumentsContract;
 16 import android.provider.MediaStore;
 17 import android.support.annotation.NonNull;
 18 import android.support.v4.app.ActivityCompat;
 19 import android.support.v4.content.ContextCompat;
 20 import android.support.v4.content.FileProvider;
 21 import android.support.v7.app.AppCompatActivity;
 22 import android.util.Log;
 23 import android.view.View;
 24 import android.widget.Button;
 25 import android.widget.ImageView;
 26 import android.widget.Toast;
 27 
 28 import java.io.File;
 29 import java.io.FileNotFoundException;
 30 import java.io.IOException;
 31 
 32 public class MainActivity extends AppCompatActivity {
 33     public static final int TAKE_PHOTO = 1;
 34 
 35     public static final int CHOOSE_PHOTO = 2;
 36 
 37     private ImageView picture;
 38 
 39     private Uri imageUri;
 40 
 41     @Override
 42     protected void onCreate(Bundle savedInstanceState) {
 43         super.onCreate(savedInstanceState);
 44         setContentView(R.layout.activity_main);
 45         Button takePhoto = (Button) findViewById(R.id.take_photo);
 46         Button chooseFromAlbum = (Button) findViewById(R.id.choose_from_album);
 47         picture = (ImageView) findViewById(R.id.picture);
 48         takePhoto.setOnClickListener(new View.OnClickListener() {
 49             @Override
 50             public void onClick(View v) {
 51                 // 创建File对象，用于存储拍照后的图片
 52                 File outputImage = new File(getExternalCacheDir(), "output_image.jpg");
 53                 try {
 54                     if (outputImage.exists()) {
 55                         outputImage.delete();
 56                     }
 57                     outputImage.createNewFile();
 58                 } catch (IOException e) {
 59                     e.printStackTrace();
 60                 }
 61                 if (Build.VERSION.SDK_INT < 24) {
 62                     imageUri = Uri.fromFile(outputImage);
 63                 } else {
 64                     imageUri = FileProvider.getUriForFile(MainActivity.this, "com.example.cameraalbumtest.fileprovider", outputImage);
 65                 }
 66                 // 启动相机程序
 67                 Intent intent = new Intent("android.media.action.IMAGE_CAPTURE");
 68                 intent.putExtra(MediaStore.EXTRA_OUTPUT, imageUri);
 69                 startActivityForResult(intent, TAKE_PHOTO);
 70             }
 71         });
 72         chooseFromAlbum.setOnClickListener(new View.OnClickListener() {
 73             @Override
 74             public void onClick(View v) {
 75                 if (ContextCompat.checkSelfPermission(MainActivity.this, Manifest.permission.WRITE_EXTERNAL_STORAGE) != PackageManager.PERMISSION_GRANTED) {
 76                     ActivityCompat.requestPermissions(MainActivity.this, new String[]{ Manifest.permission. WRITE_EXTERNAL_STORAGE }, 1);
 77                 } else {
 78                     openAlbum();
 79                 }
 80             }
 81         });
 82     }
 83 
 84     private void openAlbum() {
 85         Intent intent = new Intent("android.intent.action.GET_CONTENT");
 86         intent.setType("image/*");
 87         startActivityForResult(intent, CHOOSE_PHOTO); // 打开相册
 88     }
 89 
 90     @Override
 91     public void onRequestPermissionsResult(int requestCode, String[] permissions, int[] grantResults) {
 92         switch (requestCode) {
 93             case 1:
 94                 if (grantResults.length > 0 && grantResults[0] == PackageManager.PERMISSION_GRANTED) {
 95                     openAlbum();
 96                 } else {
 97                     Toast.makeText(this, "You denied the permission", Toast.LENGTH_SHORT).show();
 98                 }
 99                 break;
100             default:
101         }
102     }
103 
104     @Override
105     protected void onActivityResult(int requestCode, int resultCode, Intent data) {
106         switch (requestCode) {
107             case TAKE_PHOTO:
108                 if (resultCode == RESULT_OK) {
109                     try {
110                         // 将拍摄的照片显示出来
111                         Bitmap bitmap = BitmapFactory.decodeStream(getContentResolver().openInputStream(imageUri));
112                         picture.setImageBitmap(bitmap);
113                     } catch (Exception e) {
114                         e.printStackTrace();
115                     }
116                 }
117                 break;
118             case CHOOSE_PHOTO:
119                 if (resultCode == RESULT_OK) {
120                     // 判断手机系统版本号
121                     if (Build.VERSION.SDK_INT >= 19) {
122                         // 4.4及以上系统使用这个方法处理图片
123                         handleImageOnKitKat(data);
124                     } else {
125                         // 4.4以下系统使用这个方法处理图片
126                         handleImageBeforeKitKat(data);
127                     }
128                 }
129                 break;
130             default:
131                 break;
132         }
133     }
134 
135     @TargetApi(19)
136     private void handleImageOnKitKat(Intent data) {
137         String imagePath = null;
138         Uri uri = data.getData();
139         Log.d("TAG", "handleImageOnKitKat: uri is " + uri);
140         if (DocumentsContract.isDocumentUri(this, uri)) {
141             // 如果是document类型的Uri，则通过document id处理
142             String docId = DocumentsContract.getDocumentId(uri);
143             if("com.android.providers.media.documents".equals(uri.getAuthority())) {
144                 String id = docId.split(":")[1]; // 解析出数字格式的id
145                 String selection = MediaStore.Images.Media._ID + "=" + id;
146                 imagePath = getImagePath(MediaStore.Images.Media.EXTERNAL_CONTENT_URI, selection);
147             } else if ("com.android.providers.downloads.documents".equals(uri.getAuthority())) {
148                 Uri contentUri = ContentUris.withAppendedId(Uri.parse("content://downloads/public_downloads"), Long.valueOf(docId));
149                 imagePath = getImagePath(contentUri, null);
150             }
151         } else if ("content".equalsIgnoreCase(uri.getScheme())) {
152             // 如果是content类型的Uri，则使用普通方式处理
153             imagePath = getImagePath(uri, null);
154         } else if ("file".equalsIgnoreCase(uri.getScheme())) {
155             // 如果是file类型的Uri，直接获取图片路径即可
156             imagePath = uri.getPath();
157         }
158         displayImage(imagePath); // 根据图片路径显示图片
159     }
160 
161     private void handleImageBeforeKitKat(Intent data) {
162         Uri uri = data.getData();
163         String imagePath = getImagePath(uri, null);
164         displayImage(imagePath);
165     }
166 
167     private String getImagePath(Uri uri, String selection) {
168         String path = null;
169         // 通过Uri和selection来获取真实的图片路径
170         Cursor cursor = getContentResolver().query(uri, null, selection, null, null);
171         if (cursor != null) {
172             if (cursor.moveToFirst()) {
173                 path = cursor.getString(cursor.getColumnIndex(MediaStore.Images.Media.DATA));
174             }
175             cursor.close();
176         }
177         return path;
178     }
179 
180     private void displayImage(String imagePath) {
181         if (imagePath != null) {
182             Bitmap bitmap = BitmapFactory.decodeFile(imagePath);
183             picture.setImageBitmap(bitmap);
184         } else {
185             Toast.makeText(this, "failed to get image", Toast.LENGTH_SHORT).show();
186         }
187     }
188 
189 }