我正在尝试使用 asynctask 加载全屏图库菜单。我看过很多关于 asynctask 的代码来加载图像列表，但不是以画廊的形式。我希望用户在查看 main.xml 之前先查看 loadingscreen.xml。但据我了解，Asynctask 不是这样工作的。
所以：（如果我错了，请纠正我）
当画廊类文件启动时，它开始异步并在后台执行操作。
视图切换器允许用户切换视图。
部分代码取自 hello world 站点和其他参考资料。目前，我必须为加载屏幕和画廊编写单独的代码（能够运行良好）。我认为它以某种方式工作，但我错了。
GalleryLoop.java
public class GalleryLoop extends Activity {
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
// startDownload();
// Reference the Gallery view
Gallery g = (Gallery) findViewById(R.id.gallery);
g.setSpacing(2);
// Set the adapter to our custom adapter (below)
g.setAdapter(new ImageAdapter(this));
g.setOnItemClickListener(new OnItemClickListener() {
public void onItemClick(AdapterView<?> parent, View view,
int position, long id) {
switch( position )
{
case 0:
Intent newActivity0 = new Intent(GalleryLoop.this, bo_seng.class);
startActivity(newActivity0);
break;
case 1: Intent newActivity = new Intent(GalleryLoop.this, war_memorial.class);
startActivity(newActivity);
break;
}
}
});
}
// private void startDownload() {
// TODO Auto-generated method stub
// new Intent(GalleryLoop.this, LoadingScreenActivity.class);
// }
public class ImageAdapter extends BaseAdapter {
int mGalleryItemBackground;
public ImageAdapter(Context c) {
mContext = c;
}
public int getCount() {
return mImageIds.length;
}
public Object getItem(int position) {
return position;
}
public long getItemId(int position) {
return position;
}
public View getView(int position, View convertView, ViewGroup parent) {
ImageView imageView = new ImageView(mContext);
imageView.setImageResource(mImageIds[position]);
imageView.setBackgroundResource(mGalleryItemBackground);
imageView.setLayoutParams(new Gallery.LayoutParams(Gallery.LayoutParams.FILL_PARENT, Gallery.LayoutParams.FILL_PARENT));
imageView.setScaleType(ImageView.ScaleType.FIT_XY);
return imageView;
}
private Context mContext;
private Integer[] mImageIds = {
R.drawable.gallery_photo_1,
R.drawable.gallery_photo_2,
R.drawable.gallery_photo_3,
R.drawable.gallery_photo_4,
R.drawable.gallery_photo_5,
R.drawable.gallery_photo_6,
R.drawable.gallery_photo_7,
R.drawable.gallery_photo_8
};
}
}
LoadingScreenActivity.java
public class LoadingScreenActivity extends Activity
{
//creates a ViewSwitcher object, to switch between Views
private ViewSwitcher viewSwitcher;
public View ImageView;
/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
//Initialize a LoadViewTask object and call the execute() method
new LoadViewTask().execute();
}
//To use the AsyncTask, it must be subclassed
private class LoadViewTask extends AsyncTask<Void, Integer, Void>
{
//A TextView object and a ProgressBar object
private TextView tv_progress;
private ProgressBar pb_progressBar;
//Before running code in the separate thread
@Override
protected void onPreExecute()
{
//Initialize the ViewSwitcher object
viewSwitcher = new ViewSwitcher(LoadingScreenActivity.this);
/* Initialize the loading screen with data from the 'loadingscreen.xml' layout xml file.
* Add the initialized View to the viewSwitcher.*/
viewSwitcher.addView(ViewSwitcher.inflate(LoadingScreenActivity.this, R.layout.loadingscreen, null));
//Initialize the TextView and ProgressBar instances - IMPORTANT: call findViewById() from viewSwitcher.
tv_progress = (TextView) viewSwitcher.findViewById(R.id.tv_progress);
pb_progressBar = (ProgressBar) viewSwitcher.findViewById(R.id.pb_progressbar);
//Sets the maximum value of the progress bar to 100
pb_progressBar.setMax(100);
//Set ViewSwitcher instance as the current View.
setContentView(viewSwitcher);
}
//The code to be executed in a background thread.
@Override
protected Void doInBackground(Void... params)
{
/* This is just a code that delays the thread execution 4 times,
* during 850 milliseconds and updates the current progress. This
* is where the code that is going to be executed on a background
* thread must be placed.
*/
try
{
//Get the current thread's token
synchronized (this)
{
//Initialize an integer (that will act as a counter) to zero
int counter = 0;
//While the counter is smaller than four
while(counter <= 4)
{
//Wait 850 milliseconds
this.wait(850);
//Increment the counter
counter++;
//Set the current progress.
//This value is going to be passed to the onProgressUpdate() method.
publishProgress(counter*25);
}
}
}
catch (InterruptedException e)
{
e.printStackTrace();
}
return null;
}
//Update the TextView and the progress at progress bar
@Override
protected void onProgressUpdate(Integer... values)
{
//Update the progress at the UI if progress value is smaller than 100
if(values[0] <= 100)
{
tv_progress.setText("Progress: " + Integer.toString(values[0]) + "%");
pb_progressBar.setProgress(values[0]);
}
}
//After executing the code in the thread
@Override
protected void onPostExecute(Void result)
{
/* Initialize the application's main interface from the 'main.xml' layout xml file.
* Add the initialized View to the viewSwitcher.*/
viewSwitcher.addView(ViewSwitcher.inflate(LoadingScreenActivity.this, R.layout.main, null));
//Switch the Views
viewSwitcher.showNext();
//ImageView = viewSwitcher.findViewById(R.id.imageView1);
setContentView(R.layout.main);
}
}
//Override the default back key behavior
@Override
public void onBackPressed()
{
//Emulate the progressDialog.setCancelable(false) behavior
//If the first view is being shown
if(viewSwitcher.getDisplayedChild() == 0)
{
//Do nothing
return;
}
else
{
//Finishes the current Activity
super.onBackPressed();
}
}
}