android兩種方式獲取AsyncTask返回值
阿新 • • 發佈:2019-01-07
獲取AsyncTask返回值,在Activity中使用。
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佈局檔案: <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" > <ImageView android:id="@+id/im1" android:layout_width="wrap_content" android:layout_height="wrap_content" android:src="@drawable/ic_launcher" /> <ImageView android:id="@+id/im2" android:layout_width="wrap_content" android:layout_height="wrap_content" android:src="@drawable/ic_launcher" /> </LinearLayout>
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2.第一種,回撥方法方式: package com.androidwallpaper; import java.io.FileNotFoundException; import java.io.IOException; import java.io.InputStream; import java.net.HttpURLConnection; import java.net.MalformedURLException; import java.net.URL; import java.util.concurrent.ExecutorService; import java.util.concurrent.Executors; import android.net.Uri; import android.os.AsyncTask; import android.os.Bundle; import android.os.Handler; import android.os.Message; import android.app.Activity; import android.app.WallpaperManager; import android.content.Intent; import android.graphics.Bitmap; import android.graphics.BitmapFactory; import android.view.Menu; import android.view.View; import android.view.View.OnClickListener; import android.widget.Button; import android.widget.ImageView; import android.widget.ProgressBar; import android.widget.Toast; public class MainActivity extends Activity implements OnClickListener{ ImageView im1; ImageView im2; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); im1 = (ImageView) findViewById(R.id.im1); im2 = (ImageView) findViewById(R.id.im2); try { final ImageViewAsyncTask task = new ImageViewAsyncTask("http://static.oschina.net/uploads/ad/new_banner_one_ronglianyun_WrqUs.png"); task.setOnDataFinishedListener(new OnDataFinishedListener() { @Override public void onDataSuccessfully(Object data) { try { im1.setImageBitmap((Bitmap) data); } catch (Exception e) { e.printStackTrace(); } } @Override public void onDataFailed() { Toast.makeText(MainActivity.this, "載入失敗!", Toast.LENGTH_SHORT).show(); } }); task.execute(); } catch (Exception e) { e.printStackTrace(); } } class ImageViewAsyncTask extends AsyncTask<String, Integer, Bitmap> { String mUrl; OnDataFinishedListener onDataFinishedListener; public ImageViewAsyncTask(String url){ this.mUrl = url; } public void setOnDataFinishedListener( OnDataFinishedListener onDataFinishedListener) { this.onDataFinishedListener = onDataFinishedListener; } @Override protected Bitmap doInBackground(String... params) { InputStream ins = null; Bitmap bitmap = null; try { URL url = new URL(mUrl); HttpURLConnection connection = (HttpURLConnection) url.openConnection(); if(connection.getResponseCode()==HttpURLConnection.HTTP_OK){ ins = connection.getInputStream(); bitmap = BitmapFactory.decodeStream(ins); return bitmap; } } catch (MalformedURLException e) { e.printStackTrace(); } catch (IOException e) { e.printStackTrace(); }finally{ if(ins!=null){ try { ins.close(); } catch (IOException e) { e.printStackTrace(); } } } return null; } @Override protected void onPreExecute() { super.onPreExecute(); progressBar.setVisibility(View.VISIBLE); } @Override protected void onPostExecute(Bitmap result) { progressBar.setVisibility(View.GONE); if(result!=null){ onDataFinishedListener.onDataSuccessfully(result); }else{ onDataFinishedListener.onDataFailed(); } } @Override protected void onProgressUpdate(Integer... values) { super.onProgressUpdate(values); } } }
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回撥介面:
public interface OnDataFinishedListener {
public void onDataSuccessfully(Object data);
public void onDataFailed();
}
4.第二種:使用handler: 1.修改ImageViewAsyncTask: public class ImageViewAsyncTask extends AsyncTask<String, Integer, Bitmap> { String mUrl; Handler mHandler; public ImageViewAsyncTask(String url,Handler handler){ this.mUrl = url; this.mHandler = handler; } @Override protected Bitmap doInBackground(String... params) { InputStream ins = null; Bitmap bitmap = null; try { URL url = new URL(mUrl); HttpURLConnection connection = (HttpURLConnection) url.openConnection(); if(connection.getResponseCode()==HttpURLConnection.HTTP_OK){ ins = connection.getInputStream(); bitmap = BitmapFactory.decodeStream(ins); return bitmap; } } catch (MalformedURLException e) { e.printStackTrace(); } catch (IOException e) { e.printStackTrace(); }finally{ if(ins!=null){ try { ins.close(); } catch (IOException e) { e.printStackTrace(); } } } return null; } @Override protected void onPreExecute() { super.onPreExecute(); } @Override protected void onPostExecute(Bitmap result) { super.onPostExecute(result); Message msg = mHandler.obtainMessage(); if(result!=null){ msg.what = 1; msg.obj = result; }else{ msg.what = 2; } mHandler.sendMessage(msg); } @Override protected void onProgressUpdate(Integer... values) { super.onProgressUpdate(values); } } 2.呼叫方式: ImageViewAsyncTask task2 = new ImageViewAsyncTask("http://static.oschina.net/uploads/ad/new_banner_one_ronglianyun_WrqUs.png", handler); task2.execute(); Handler handler = new Handler(){ @Override public void handleMessage(Message msg) { switch (msg.what) { case 1: Bitmap bitmap = (Bitmap) msg.obj; im2.setImageBitmap(bitmap); break; default: break; } } };