android 获取图库中展示到界面中

<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"
    tools:context="com.example.useimage.MainActivity" >

    <Button
        android:onClick="selectImage"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:text="选择一个图片" />
    
     <ImageView 
         android:id="@+id/iv"
         android:layout_width="fill_parent"
        android:layout_height="fill_parent"
         />

</LinearLayout>

package com.example.useimage;

import android.content.Intent;
import android.net.Uri;
import android.os.Bundle;
import android.support.v7.app.ActionBarActivity;
import android.view.View;
import android.widget.ImageView;


public class MainActivity extends ActionBarActivity {

    private ImageView iv;
    
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        
        iv = (ImageView)findViewById(R.id.iv);
        
    }
    
    
    public void selectImage(View view)
    {
        
        Intent intent = new Intent();
        intent.setAction(Intent.ACTION_PICK);
        intent.setType("image/*");
        startActivityForResult(intent, 0);
        
    }

    @Override
    protected void onActivityResult(int arg0, int arg1, Intent data) {
        
        if(data!=null)
        {
            
            Uri uri = data.getData();
            iv.setImageURI(uri);
        }
        super.onActivityResult(arg0, arg1, data);
    }


}