对于Handler处理机制来说
当创建了一个子线程想去更改主线程的组件的时候是不被允许的,所以就可以通过handler方式来进行,还有急速message方法中有延时发送的请求,可以完成倒计时的效果
private TextView xiaoxi;
private ProgressBar times;
final int TIME=60;//定义时间长度
final int TIMEMSG=0x001;
private int mprogress=0;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_duo);
xiaoxi = findViewById(R.id.xiaoxi);
times = findViewById(R.id.time);
Button xia = findViewById(R.id.xia);
handler1.sendEmptyMessage(TIMEMSG);
final Handler handler=new Handler(){
@Override
public void handleMessage(@NonNull Message msg) {
super.handleMessage(msg);
if(msg.what==0x123)
{
xiaoxi.setText("变一条信息");
}
}
};
xia.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
Thread thread=new Thread(new Runnable() {
@Override
public void run() {
handler.sendEmptyMessage(0x123);//发送空消息
}
});
thread.start();
}
});
具体步骤
1.创建对象
final Handler handler=new Handler(){
@Override
public void handleMessage(@NonNull Message msg) {
super.handleMessage(msg);
if(msg.what==0x123)
{
xiaoxi.setText("变一条信息");
}
}
};
通过匿名内部类来实现的,其中handlemessage方法时时刻刻在监听着有无消息的传入。
2.发送消息
Thread thread=new Thread(new Runnable() {
@Override
public void run() {
handler.sendEmptyMessage(0x123);//发送空消息
}
});
thread.start();
这样就完事了;
另外获取message对象也是可行的;
Message message2=handler2.obtainMessage();
message2.what=0x7;
handler1.sendMessage(message2);
Looper.loop();
进阶
Handler handler1=new Handler()
{
@Override
public void handleMessage(@NonNull Message msg) {
super.handleMessage(msg);
if(TIME-mprogress>0)
{
mprogress++;
times.setProgress(TIME-mprogress);
handler1.sendEmptyMessageDelayed(TIMEMSG,1000);
}
else
{
Toast.makeText(duo.this,"时间到",Toast.LENGTH_SHORT).show();;
}
}
};
秒表实现
还有僵尸loop看下,就是在子线程里不能创建handler对象,需要在子线程里手动先创建loop对象的;