求助 MyAsynTask實(shí)例化時ImageTest的構(gòu)造函數(shù)沒有執(zhí)行，mProgressBar.setVisibility(View.VISIBLE);這一句報空指針異常
public class MainActivity extends ActionBarActivity {
? ? @Override
? ? protected void onCreate(Bundle savedInstanceState) {
? ? ? ? super.onCreate(savedInstanceState);
? ? ? ?// Log.v("tag","執(zhí)行mainactivity");
? ? ? ? setContentView(R.layout.activity_main);
? ? ? ?
? ? ? ?// ImageTest textd= new ImageTest();
? ? ? ? MyAsynTask task =new ImageTest().new MyAsynTask();
? ? ? ? task.execute();
? ? ? ??
? ? ?}
? ? public void LOADIMAGE(View view){
? ? startActivity(new Intent(this,ImageTest.class));
? ? }
}
public ?class ImageTest extends Activity{
private ImageView mImageView;
private ProgressBar mProgressBar;
private static String URL="http://img.my.csdn.net/uploads/201504/12/1428806103_9476.png";
@Override
protected void onCreate(Bundle savedInstanceState) {
// TODO Auto-generated method stub
super.onCreate(savedInstanceState);
setContentView(R.layout.image);
mImageView=(ImageView) findViewById(R.id.imageView);
mProgressBar=(ProgressBar) findViewById(R.id.progressBar);
Log.v("tag","構(gòu)造函數(shù)已執(zhí)行");
//設(shè)置傳遞進(jìn)去的參數(shù)
new MyAsynTask().execute(URL);
}
?class ?MyAsynTask extends AsyncTask<String,Void,Bitmap>{
@Override
protected void onPreExecute() {
// TODO Auto-generated method stub
super.onPreExecute();
Log.v("tag","這里還好");
mProgressBar.setVisibility(View.VISIBLE);
}
@Override
protected void onPostExecute(Bitmap bitmap) {
// TODO Auto-generated method stub
super.onPostExecute(bitmap);
mProgressBar.setVisibility(View.GONE);
mImageView.setImageBitmap(bitmap);
}
@Override
protected Bitmap doInBackground(String... arg0) {
// TODO Auto-generated method stub
//獲取傳遞進(jìn)來的參數(shù)
Log.v("tag","傳入?yún)?shù)長度"+arg0.length);
String url =arg0[0];
Bitmap bitmap=null;
URLConnection connection;
InputStream is;
try {
connection =new URL(url).openConnection();
is=connection.getInputStream();
BufferedInputStream bis=new BufferedInputStream(is);
Thread.sleep(3000);
bitmap=BitmapFactory.decodeStream(bis);//將輸入流解析為bitmap
is.close();
bis.close();
} catch (MalformedURLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
return bitmap;
}
}
}
求問哪里出了問題？
