android从相册中获取照片出错。

 package com.example.choosepictest;

import java.io.File;
import java.io.FileNotFoundException;
import java.io.IOException;
import android.support.v7.app.ActionBarActivity;
import android.support.v7.app.ActionBar;
import android.support.v4.app.Fragment;
import android.annotation.SuppressLint;
import android.annotation.TargetApi;
import android.app.Activity;
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.Bundle;
import android.os.Environment;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.view.View.OnClickListener;
import android.view.ViewGroup;
import android.widget.Button;
import android.widget.ImageView;
import android.widget.Toast;
import android.os.Build;
import android.provider.DocumentsContract.Document;
import android.provider.DocumentsContract;
import android.provider.MediaStore;
import android.provider.MediaStore.Images.Media;

public class MainActivity extends Activity {

    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_photo);
        picture=(ImageView)findViewById(R.id.picture);
        takePhoto.setOnClickListener(new OnClickListener() {

            @Override
            public void onClick(View arg0) {
                // TODO Auto-generated method stub
                File outPutImage=new File(Environment.getExternalStorageDirectory(), "output_image.jpg");
                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);
            }
        });
        chooseFromAlbum=(Button)findViewById(R.id.choose_from_album);
        chooseFromAlbum.setOnClickListener(new OnClickListener() {

            @Override
            public void onClick(View arg0) {
                // TODO Auto-generated method stub
                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) {
        // TODO Auto-generated method stub
        switch(requestCode)
        {
        case TAKE_PHOTO:
            if(resultCode==RESULT_OK)
            {
                Intent intent=new Intent("com.android.camera.action.CROP");
                intent.setDataAndType(imageUri, "image/*");
                intent.putExtra("scale", false);
                intent.putExtra(MediaStore.EXTRA_OUTPUT, imageUri);
                startActivityForResult(intent, CROP_PHOTO);
            }
            break;
        case CROP_PHOTO:
            if(resultCode==RESULT_OK)
            {
                try {
                    Bitmap bitmap=BitmapFactory.decodeStream
                            (getContentResolver().openInputStream(imageUri));
                    picture.setImageBitmap(bitmap);
                } catch (FileNotFoundException e) {
                    // TODO Auto-generated catch block
                    e.printStackTrace();
                }


            }
            break;
        case CHOOSE_PHOTO:
            if(resultCode==RESULT_OK)
            {
                if(Build.VERSION.SDK_INT>=19)
                {
                    handleImageOnKitKat(data);
                }
                else
                {
                    handleImageBeforeKitKat(data);
                }
            }
            break;
            default:
                break;
        }

    }
    private void handleImageBeforeKitKat(Intent data) {
        // TODO Auto-generated method stub
        Uri uri=data.getData();
        String imagePath=getImagePath(uri, null);
        dispalyImage(imagePath);
    }



    @TargetApi(Build.VERSION_CODES.KITKAT) @SuppressLint("NewApi") 
    private void handleImageOnKitKat(Intent data) {
        // TODO Auto-generated method stub

        String imagePath =null;
        Uri uri=data.getData();

        if(DocumentsContract.isDocumentUri(this, uri)){

            String docId=DocumentsContract.getDocumentId(uri);
            if("com.android.providers.media.documents".equals(uri.getAuthority()))
            {

                String id=docId.split(":")[1];
                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())){

            imagePath=getImagePath(uri, null);
        }

        dispalyImage(imagePath);
    }
    private void dispalyImage(String imagePath) {
        // TODO Auto-generated method stub
        if(imagePath!=null)
        {
            Bitmap bitmap =BitmapFactory.decodeFile(imagePath);
            picture.setImageBitmap(bitmap);
        }else
        {
            Toast.makeText(this, "获取图像失败", Toast.LENGTH_SHORT).show();
        }
    }
    private String getImagePath(Uri uri, String selection) {
        // TODO Auto-generated method stub

        String path=null;
        Cursor cursor=getContentResolver().query(uri, null, selection, null, null);
        if(cursor!=null)
        {
            if(cursor.moveToFirst()){
                path=cursor.getString(cursor.getColumnIndex(Media.DATA));
            }
            cursor.close();
        }

        return path;
    }

}

布局

 <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    >
    <Button 
        android:id="@+id/take_photo"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="Take Photo"
        />
    <Button 
        android:id="@+id/choose_from_album"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="Choose From Album"/>

    <ImageView 
        android:id="@+id/picture"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="center_horizontal"/>
</LinearLayout>

权限已声明，当case CHOOSE_PHOTO:时进入handleimangeonKitkat后的if语句一个都不会进入