ProgressBar、Handler的简单使用

<1.XML布局文件>

<?xml version="1.0" encoding="utf-8"?>
<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">

    <ProgressBar
        android:layout_marginTop="10dp"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        style="?android:attr/progressBarStyleHorizontal"
        android:id="@+id/progressbar"
        android:max="100"/>
    <Button
        android:id="@+id/star"
        android:layout_width="80dp"
        android:layout_height="60dp"
        android:text="开始"
        android:gravity="center"
        android:textSize="24.0sp"/>
</LinearLayout>

<2.源代码>

public class MainActivity extends AppCompatActivity {

    //进度条
    private ProgressBar progressBar;
    //开始按钮
    private Button button;
    //设置进度条的初始值
    private int counnt=0;
    //子线程与主线程通信
    private Handler handler;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        init();
        //对开始按钮的监听
        button.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                //调用线程用来通信
                start();
            }
        });

        //实例化handler与主线程通信  <特别注意，只能在主线程实例化>
        handler=new Handler(){
            @Override
            public void handleMessage(Message msg) {
                //判断是哪个子线程发来的信息
                switch (msg.what){
                    case 1:
                        progressBar.setProgress((Integer) msg.obj);
                        break;
                }
            }
        };

    }

    //实例化控件
    private void init(){
        progressBar= (ProgressBar) findViewById(R.id.progressbar);
        button= (Button) findViewById(R.id.star);
    }

    //开启一个子线程
    private void start(){
        new Thread(){
            @Override
            public void run() {
                while (counnt<=100){
                    Message msg=new Message();
                    //给当前线程添加标签
                    msg.what=1;
                    //赋值
                    msg.obj=counnt;
                    //发送信息
                    handler.sendMessage(msg);
                    counnt++;
                    try {
                        //每赋值一次休眠200毫秒
                        sleep(200);
                    } catch (InterruptedException e) {
                        e.printStackTrace();
                    }
                }
            }
        }.start();
    }

}