如何在android中的画廊屏幕上显示对话框？

Question

我正在从图库中选择一个图像并移动到MainActivity以显示所选图像。我需要在图库中单击图像并显示它3秒钟后才能在图库屏幕上显示进度对话框然后我应该移动到MainActivity来显示所选择的图像。我在这里通过第一个活动而不是通过画廊屏幕获得对话框。我应该如何实现这个目标？我花了很多时间来解决这个问题。但是我没有得到它。请帮助我。我在这里提供更新的示例代码。

import android.app.Activity;
import android.app.ProgressDialog;
import android.content.Intent;
import android.database.Cursor;
import android.graphics.Bitmap;
import android.net.Uri;
import android.os.AsyncTask;
import android.os.Bundle;
import android.provider.MediaStore;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.ImageButton;




public class LauncherActivity extends Activity 
{
 private static int RESULT_LOAD_IMAGE = 2;
 ImageButton gallery;
 Bitmap bitmap_for_gallery;
 String picturePath;
 ProgressDialog dialog;;
 Uri selectedImage;

 protected void onCreate(Bundle paramBundle)
{
super.onCreate(paramBundle);
setContentView(R.layout.launcher);
gallery = (ImageButton)findViewById(R.id.select_photo);

gallery.setOnClickListener(new OnClickListener() {

    @Override
    public void onClick(View v) {
        // TODO Auto-generated method stub          
        Intent gallery_intent = new Intent(Intent.ACTION_PICK, android.provider.MediaStore.Images.Media.EXTERNAL_CONTENT_URI);
        startActivityForResult(gallery_intent, RESULT_LOAD_IMAGE);

    }
});
  }
      protected void onActivityResult(int requestCode, int resultCode, final Intent data) {
    super.onActivityResult(requestCode, resultCode, data);
      if (requestCode == RESULT_LOAD_IMAGE && resultCode == RESULT_OK && null != data) {

      AsyncTask<String, Void, String> updateTask = new AsyncTask<String, Void, String>(){


            @Override

            protected void onPreExecute() {
              selectedImage = data.getData();
                dialog = new ProgressDialog(LauncherActivity.this);
                dialog.setMessage("Loading...");
                dialog.show();
            }
            protected String doInBackground(String... params) {
                // TODO Auto-generated method stub
                String[] filePathColumn = { MediaStore.Images.Media.DATA };
                  Cursor cursor = getContentResolver().query(selectedImage,filePathColumn, null, null, null);
                  cursor.moveToFirst();
                  int columnIndex = cursor.getColumnIndex(filePathColumn[0]);
                   picturePath = cursor.getString(columnIndex);
                  cursor.close();
                return null;
            }
            protected void onPostExecute(String result) {
                Intent intent = new Intent(LauncherActivity.this, MainActivity.class);
                intent.putExtra("path", picturePath); 
                startActivity(intent);
                dialog.dismiss();
            }

        };

        updateTask.execute();
  }
 }
}

我的MainActivity是

 import android.app.Activity;
 import android.graphics.Bitmap;
 import android.graphics.BitmapFactory;
 import android.os.Bundle;
 import android.widget.FrameLayout;
 import android.widget.ImageView;
 import android.widget.RelativeLayout.LayoutParams;


 public class MainActivity extends Activity {
 ImageView background;
 Bitmap transfered;
  FrameLayout.LayoutParams layoutParams;

@SuppressWarnings("deprecation")
@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
 background=(ImageView)findViewById(R.id.imageView1);

 layoutParams=new FrameLayout.LayoutParams(LayoutParams.FILL_PARENT,LayoutParams.FILL_PARENT);
 Bundle extras = getIntent().getExtras();

    String picturePath=extras.getString("path");
     transfered=BitmapFactory.decodeFile(picturePath);  
 background.setImageBitmap(transfered); 
 background.setAdjustViewBounds(true);
 background.setLayoutParams(layoutParams);
 }

}