Android应用中怎么获取手机里的图片

public class MainActivity extends Activity { 

//查看图片按钮 
  private Button look; 
  private Button add; 
//显示图片名称的list 
  ListView show_list; 
  ArrayList names = null; 
  ArrayList descs= null; 
  ArrayList fileNames = null; 
  @Override 
  protected void onCreate(Bundle savedInstanceState) { 
    super.onCreate(savedInstanceState); 
    setContentView(R.layout.activity_main); 
    look = (Button) findViewById(R.id.look); 
    add = (Button) findViewById(R.id.add); 
    show_list = (ListView) findViewById(R.id.show_list); 
    look.setOnClickListener(new View.OnClickListener() { 
      @Override 
      public void onClick(View view) { 
        names = new ArrayList(); 
        descs = new ArrayList(); 
        fileNames = new ArrayList(); 
        Cursor cursor = getContentResolver().query( 
            MediaStore.Images.Media.EXTERNAL_CONTENT_URI, null, null, null, null); 
        while (cursor.moveToNext()) { 
          //获取图片的名称 
          String name = cursor.getString(cursor.getColumnIndex(MediaStore.Images.Media.DISPLAY_NAME)); 
          //获取图片的生成日期 
          byte[] data = cursor.getBlob(cursor.getColumnIndex(MediaStore.Images.Media.DATA)); 
          //获取图片的详细信息 
          String desc = cursor.getString(cursor.getColumnIndex(MediaStore.Images.Media.DESCRIPTION)); 
          names.add(name); 
          descs.add(desc); 
          fileNames.add(new String(data, 0, data.length - 1)); 
        } 
        List<Map<String, Object>> listItems = new ArrayList<>(); 
        for (int i = 0; i < names.size(); i++) { 
          Map<String, Object> map = new HashMap<>(); 
          map.put("name", names.get(i)); 
          map.put("desc", descs.get(i)); 
          listItems.add(map); 
        } 
        //设置adapter 
        SimpleAdapter adapter = new SimpleAdapter(MainActivity.this, listItems, 
            R.layout.line, new String[]{"name", "desc"}, new int[]{R.id.name, R.id.desc}); 
 
        show_list.setAdapter(adapter); 
      } 
    }); 
 
    ///list的点击事件 
  show_list.setOnItemClickListener(new AdapterView.OnItemClickListener() { 
    @Override 
    public void onItemClick(AdapterView<&#63;> adapterView, View view, int i, long l) { 
      View viewDiag = getLayoutInflater().inflate(R.layout.view,null); 
      ImageView image = (ImageView)viewDiag.findViewById(R.id.image); 
      image.setImageBitmap(BitmapFactory.decodeFile((String) fileNames.get(i))); 
      new AlertDialog.Builder(MainActivity.this).setView(viewDiag) 
          .setPositiveButton("确定",null).show(); 
    } 
  }); 
  } 
} 

<!--获取手机存储卡权限-->
<uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE"/>