（1）
<RelativeLayout 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:paddingBottom="@dimen/activity_vertical_margin"
android:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
tools:context=".MainActivity" > <TextView
android:id="@+id/textView1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="进度条的使用：" /> <ProgressBar
android:id="@+id/progressBar1"
style="?android:attr/progressBarStyleHorizontal"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignLeft="@+id/button1"
android:layout_alignRight="@+id/button1"
android:layout_below="@+id/textView1"
android:layout_marginTop="30dp" /> <Button
android:id="@+id/button1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignLeft="@+id/textView1"
android:layout_below="@+id/progressBar1"
android:layout_marginLeft="74dp"
android:layout_marginTop="146dp"
android:text="下载图片" /></RelativeLayout>
（2）
package com.example.progressbar;import android.app.Activity;
import android.os.AsyncTask;
import android.os.Bundle;
import android.view.Menu;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.ProgressBar;public class MainActivity extends Activity {private Button button1;
private ProgressBar progressBar1;@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
button1 = (Button) this.findViewById(R.id.button1);
progressBar1 = (ProgressBar) this.findViewById(R.id.progressBar1);progressBar1.setMax(100);// 设置最大值为100button1.setOnClickListener(new OnClickListener() {@Override
public void onClick(View v) {
new MyTask().execute();
}
});
}class MyTask extends AsyncTask<Void, Integer, Void> {
@Override
protected void onProgressUpdate(Integer... values) {
super.onProgressUpdate(values);
progressBar1.setProgress(values[0]);
}@Override
protected Void doInBackground(Void... params) {int i = 1;
while (i <= 100) {
try {
Thread.sleep(500);
} catch (Exception e) {
// TODO: handle exception
}
publishProgress(i);
i++;
}
return null;
}
}@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.main, menu);
return true;
}}
（3）演示效果
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