android利用handler实现倒计时功能

本文实例为大家分享了android利用handler实现倒计时的具体代码，供大家参考，具体内容如下

xml

<?xml version='1.0' encoding='utf-8'?><androidx.constraintlayout.widget.ConstraintLayout xmlns:android='http://schemas.android.com/apk/res/android' xmlns:app='http://schemas.android.com/apk/res-auto' xmlns:tools='http://schemas.android.com/tools' android:layout_width='match_parent' android:layout_height='match_parent' tools:context='.MainActivity'> <TextView android: android:layout_width='wrap_content' android:layout_height='wrap_content' android:text='Hello World!' app:layout_constraintBottom_toBottomOf='parent' app:layout_constraintLeft_toLeftOf='parent' app:layout_constraintRight_toRightOf='parent' app:layout_constraintTop_toTopOf='parent' /></androidx.constraintlayout.widget.ConstraintLayout>

java

package com.tcy.handlertest;import androidx.annotation.NonNull;import androidx.appcompat.app.AppCompatActivity;import android.os.Bundle;import android.os.Handler;import android.os.Message;import android.widget.TextView;import java.lang.ref.WeakReference;public class MainActivity extends AppCompatActivity { /** * 倒计时标记handler code */ public static final int COUNT_DOWN_CODE = 10001; /** * 倒计时最大值 */ public static final int MAX_COUNT = 10; /** * 倒计时间隔 */ public static final int DELAY_MILLIS = 1000; TextView textView; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); textView = findViewById(R.id.text); CountdownTimeHandler handler = new CountdownTimeHandler(this); Message message = Message.obtain(); message.what = COUNT_DOWN_CODE; message.arg1 = MAX_COUNT; handler.sendMessageDelayed(message, DELAY_MILLIS); } public static class CountdownTimeHandler extends Handler { //弱引用加在上下文上面 final WeakReference<MainActivity> weakReference; //这个方法要改一下，这样就能直接传进来上下文 public CountdownTimeHandler(MainActivity activity) { this.weakReference = new WeakReference<>(activity); } @Override public void handleMessage(@NonNull Message msg) { super.handleMessage(msg); //得到上下文 MainActivity activity = weakReference.get(); switch (msg.what) { case COUNT_DOWN_CODE: int value = msg.arg1; activity.textView.setText(String.valueOf(value--)); if (value >= 0) { //再把value发出去 Message message = Message.obtain(); message.what = COUNT_DOWN_CODE; message.arg1 = value; sendMessageDelayed(message, DELAY_MILLIS); } break; } } }}

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