进度条 ProgressBar的简单运用

进度条 ProgressBar
1 常用属性
style=”?android:attr/progressBarStyleHorizontal” 默认为圆形
android:progress=”33”
android:max=”100”
线程休眠
Thread.sleep(100);//抛异常
SystemClock.sleep(100);//不会抛异常

2 线程注意事项：
不能在主线程中执行耗时的操作，只能在子线程中操作
另外，在子线程中不能操作主线程中的控件(ProgressBar除外)

 SubThread->MainThread    错误

3 Handler(重点、面试问得比较多)
用于线程之间的通信，比如：主线程与子线程

.4 线程小结
SubThread->MainThread 错误
SubThread->Handler->MainThread 正确

public class MainActivity extends AppCompatActivity {
    private ProgressBar pb_main_pb1;
    private int progress=0;
    private TextView tv_main_tv1;
    private MyHandler myHandler=new MyHandler();


    private int code=1;
    private class MyHandler extends Handler{
        @Override
        public void handleMessage(Message msg) {
            super.handleMessage(msg);
            if (code==msg.what){
                progress++;
                pb_main_pb1.setProgress(progress);
                tv_main_tv1.setText(progress+"%");
            }

        }
    }
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        pb_main_pb1=this.findViewById(R.id.pb_main_pb1);
        tv_main_tv1=this.findViewById(R.id.tv_main_tv1);
    }



    public void setProgress(View view) {
        if (0==progress){
            new MyThread().start();
        }
    }
    private class MyThread extends  Thread{
        @Override
        public void run() {
            super.run();
            while(true){
                try {
                    Thread.sleep(100);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
                if (progress==100){
                    progress=0;
                    break;
                }
                Message msg=new Message();
                msg.what=1;
                myHandler.sendMessage(msg);


            }
        }
    }
}