Android学习笔记之ProgressBar案例分析

（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100

		button1.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