android从系统图库中取图片的实例代码

package com.easymorse.gallery;
import java.io.File;
import android.app.Activity;
import android.content.Intent;
import android.graphics.drawable.Drawable;
import android.net.Uri;
import android.os.Bundle;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
public class GalleryActivity extends Activity {
 private static int SELECT_PICTURE;
 private File tempFile;
 Button button;
 /** Called when the activity is first created. */
 @Override
 public void onCreate(Bundle savedInstanceState) {
  super.onCreate(savedInstanceState);
  this.tempFile=new File("/sdcard/a.jpg");
  button = new Button(this);
  button.setText("获取图片");
  button.setOnClickListener(new OnClickListener() {
   @Override
   public void onClick(View v) {
    Intent intent = new Intent(Intent.ACTION_GET_CONTENT);
    intent.setType("image/*");
    intent.putExtra("crop", "true");
    // intent.putExtra("aspectX", 1);
    // intent.putExtra("aspectY", 2);
    intent.putExtra("output", Uri.fromFile(tempFile));
    intent.putExtra("outputFormat", "JPEG");
    startActivityForResult(Intent.createChooser(intent, "选择图片"),
      SELECT_PICTURE);
   }
  });
  setContentView(button);
 }
 @Override
 protected void onActivityResult(int requestCode, int resultCode, Intent data) {
  if (resultCode == RESULT_OK) {
   if (requestCode == SELECT_PICTURE) {
    button.setBackgroundDrawable(Drawable.createFromPath(tempFile
      .getAbsolutePath()));
   }
  }
 }
}