Android——使用handler實現輪播圖

xml文件

<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.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">

    <Button
        android:id="@+id/change"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginStart="8dp"
        android:layout_marginLeft="8dp"
        android:layout_marginTop="8dp"
        android:text="Button"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

    <TextView
        android:id="@+id/text"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginStart="8dp"
        android:layout_marginLeft="8dp"
        android:layout_marginTop="8dp"
        android:text="TextView"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/change" />

    <ImageView
        android:id="@+id/imageView"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginStart="8dp"
        android:layout_marginLeft="8dp"
        android:layout_marginTop="8dp"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/text"
        tools:srcCompat="@tools:sample/avatars[10]" />
</android.support.constraint.ConstraintLayout>

MainActivity.java

package com.example.threadtest;

import android.os.Handler;
import android.os.Message;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.ImageView;
import android.widget.TextView;

import static java.lang.Thread.sleep;

public class MainActivity extends AppCompatActivity {
    public static final int UPDATA = 1;
    private TextView textView;
    private Button button;
    private Handler hander;
    private ImageView imageView;
    private String[] strings={"1","2","3"};
    private int[] imageViews={R.mipmap.a,R.mipmap.b,R.mipmap.c};
    int index=0;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        textView=findViewById(R.id.text);
        button=findViewById(R.id.change);
        imageView=findViewById(R.id.imageView);
        hander=new Handler(){
            @Override
            public void handleMessage(Message msg) {
                switch (msg.what){
                    case UPDATA:
                        index=index%3;
                        textView.setText(strings[index]);
                        imageView.setImageResource(imageViews[index]);
                        index++;
                }
            }
        };

        button.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
               final Thread thread= new Thread(new Runnable() {
                    @Override
                    public void run() {
                        while (true) {
                            Message message = new Message();
                            message.what = UPDATA;
                            hander.sendMessage(message);
                            try {
                                sleep(1000);
                            } catch (InterruptedException e) {
                                e.printStackTrace();
                            }
                        }
                    }
                });
               thread.start();
            }
        });

    }
}

1. Message是線程之間傳遞的消息，攜帶少量信息，int類型的what，arg1,arg2和object類型的obj。
2. Hander是發送以及處理消息的，發送消息使用sendMessage(),最終處理消息在handleMessage()中。