Android入门教程 AsyncTask的使用及execute和executeOnExecutor方法
AsyncTask的使用分为三大步。
- 创建一个子类继承AsyncTask;
- 在子类中实现如下方法
doInBackground()
onProgressUpdate()
onPostExecute() - 调用execute方法（或executeOnExecutor方法）
实例：通过AsyncTask模拟下载文件
- 通过execute方法模拟串行下载
- 通过executeOnExecutor方法模拟并行下载
实验结果总结
通过这个实例的演示，我们可以看到使用execute方法启动时，下载任务是串行的，即必须等第一个下载完成后才能下载第二个；使用executeOnExecutor启动时，可以进行并行执行，所有任务可以同步进行。
请看下面的这张截图，我是在第三个完成、第4个刚启动时，同时启动了第6个，之后又同时启动了第7、8、9、10个任务。
注意：同一时间只能同时进行5个任务
布局文件展示
"http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="wrap_content" >
"match_parent"
android:layout_height="match_parent"
android:orientation="vertical" >
id="@+id/p1"
style="?android:attr/progressBarStyleHorizontal"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_weight="1"
android:max="100" />
id="@+id/p2"
style="?android:attr/progressBarStyleHorizontal"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_weight="1"
android:max="100" />
id="@+id/p3"
style="?android:attr/progressBarStyleHorizontal"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_weight="1"
android:max="100" />
id="@+id/p4"
style="?android:attr/progressBarStyleHorizontal"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_weight="1"
android:max="100" />
id="@+id/p5"
style="?android:attr/progressBarStyleHorizontal"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_weight="1"
android:max="100" />
Java代码展示
public class DownLoadActivity extends Activity implements OnClickListener{
private Button btn1;
private Button btn2;
private Button btn3;
private Button btn4;
private Button btn5;
private Button btn6;
private Button btn7;
private Button btn8;
private Button btn9;
private Button btn10;
private ProgressBar p1;
private ProgressBar p2;
private ProgressBar p3;
private ProgressBar p4;
private ProgressBar p5;
private ProgressBar p6;
private ProgressBar p7;
private ProgressBar p8;
private ProgressBar p9;
private ProgressBar p10;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_down_load);
bindID();
}
private void bindID() {
btn1 = (Button) findViewById(R.id.b1);
btn2 = (Button) findViewById(R.id.b2);
btn3 = (Button) findViewById(R.id.b3);
btn4 = (Button) findViewById(R.id.b4);
btn5 = (Button) findViewById(R.id.b5);
btn6 = (Button) findViewById(R.id.b6);
btn7 = (Button) findViewById(R.id.b7);
btn8 = (Button) findViewById(R.id.b8);
btn9 = (Button) findViewById(R.id.b9);
btn10 = (Button) findViewById(R.id.b10);
p1 = (ProgressBar) findViewById(R.id.p1);
p2 = (ProgressBar) findViewById(R.id.p2);
p3 = (ProgressBar) findViewById(R.id.p3);
p4 = (ProgressBar) findViewById(R.id.p4);
p5 = (ProgressBar) findViewById(R.id.p5);
p6 = (ProgressBar) findViewById(R.id.p6);
p7 = (ProgressBar) findViewById(R.id.p7);
p8 = (ProgressBar) findViewById(R.id.p8);
p9 = (ProgressBar) findViewById(R.id.p9);
p10 = (ProgressBar) findViewById(R.id.p10);
btn1.setOnClickListener(this);
btn2.setOnClickListener(this);
btn3.setOnClickListener(this);
btn4.setOnClickListener(this);
btn5.setOnClickListener(this);
btn6.setOnClickListener(this);
btn7.setOnClickListener(this);
btn8.setOnClickListener(this);
btn9.setOnClickListener(this);
btn10.setOnClickListener(this);
}
class DownloadTask extends AsyncTask{
@Override
protected String doInBackground(Integer... params) {
System.out.println(params[0]+"......启动");
String result=params[0]+"";
int count = 0;
while(count<10){
try {
Thread.sleep(1000);
} catch (InterruptedException e) {
e.printStackTrace();
}
count++;
publishProgress(count,params[0]);
}
return result;
}
@Override
protected void onPostExecute(String result) {
super.onPostExecute(result);
System.out.println(result+"......完成");
int flag = Integer.parseInt(result);
switch (flag) {
case 1:
btn1.setText("下载完成");
btn1.setEnabled(false);
break;
case 2:
btn2.setText("下载完成");
btn2.setEnabled(false);
break;
case 3:
btn3.setText("下载完成");
btn3.setEnabled(false);
break;
case 4:
btn4.setText("下载完成");
btn4.setEnabled(false);
break;
case 5:
btn5.setText("下载完成");
btn5.setEnabled(false);
break;
case 6:
btn6.setText("下载完成");
btn6.setEnabled(false);
break;
case 7:
btn7.setText("下载完成");
btn7.setEnabled(false);
break;
case 8:
btn8.setText("下载完成");
btn8.setEnabled(false);
break;
case 9:
btn9.setText("下载完成");
btn9.setEnabled(false);
break;
case 10:
btn10.setText("下载完成");
btn10.setEnabled(false);
break;
default:
break;
}
}
@Override
protected void onProgressUpdate(Integer... values) {
super.onProgressUpdate(values);
int flag = values[1];
switch (flag) {
case 1:
p1.setProgress(values[0]*10);
break;
case 2:
p2.setProgress(values[0]*10);
break;
case 3:
p3.setProgress(values[0]*10);
break;
case 4:
p4.setProgress(values[0]*10);
break;
case 5:
p5.setProgress(values[0]*10);
break;
case 6:
p6.setProgress(values[0]*10);
break;
case 7:
p7.setProgress(values[0]*10);
break;
case 8:
p8.setProgress(values[0]*10);
break;
case 9:
p9.setProgress(values[0]*10);
break;
case 10:
p10.setProgress(values[0]*10);
break;
default:
break;
}
}
}
@SuppressLint("NewApi")
@Override
public void onClick(View v) {
switch (v.getId()) {
case R.id.b1:
DownloadTask t1 = new DownloadTask();
t1.execute(1);
break;
case R.id.b2:
DownloadTask t2 = new DownloadTask();
t2.execute(2);
break;
case R.id.b3:
DownloadTask t3 = new DownloadTask();
t3.execute(3);
break;
case R.id.b4:
DownloadTask t4 = new DownloadTask();
t4.execute(4);
break;
case R.id.b5:
DownloadTask t5 = new DownloadTask();
t5.execute(5);
break;
case R.id.b6:
DownloadTask t6 = new DownloadTask();
t6.executeOnExecutor(AsyncTask.THREAD_POOL_EXECUTOR, 6);
break;
case R.id.b7:
DownloadTask t7 = new DownloadTask();
t7.executeOnExecutor(AsyncTask.THREAD_POOL_EXECUTOR, 7);
break;
case R.id.b8:
DownloadTask t8 = new DownloadTask();
t8.executeOnExecutor(AsyncTask.THREAD_POOL_EXECUTOR, 8);
break;
case R.id.b9:
DownloadTask t9 = new DownloadTask();
t9.executeOnExecutor(AsyncTask.THREAD_POOL_EXECUTOR, 9);
break;
case R.id.b10:
DownloadTask t10 = new DownloadTask();
t10.executeOnExecutor(AsyncTask.THREAD_POOL_EXECUTOR, 10);
break;
default:
break;
}
}
}