一手遮天 Android - Activity: Activity 的生命周期,监听返回键,监听当前 activity 的离开事件

项目地址 https://github.com/webabcd/AndroidDemo
作者 webabcd

一手遮天 Android - Activity: Activity 的生命周期,监听返回键,监听当前 activity 的离开事件

示例如下:

/activity/ActivityDemo1.java

/**
 * Activity 的生命周期
 *
 * 详见 @drawable/img_activity_lifecycle 生命周期图,大概说明一下,如下
 * 1、新创建的 onCreate() -> onStart() -> onResume()
 * 2、失去焦点但是可见 onPause(),从此状态恢复时 onResume()
 * 3、失去焦点且不可见 onPause() -> onStop(),从此状态恢复时 onStart() -> onResume()
 * 4、彻底被销毁 onPause() -> onStop() -> onDestroy(),从此状态恢复就是重新创建 onCreate() -> onStart() -> onResume()
 *
 *
 * 举个例子,打开 ActivityDemo1,然后点击按钮跳转到 ActivityDemo1_2,再点击按钮关闭 ActivityDemo1_2,则会显示 ActivityDemo1,此场景相关的生命周期日志如下
 * ActivityDemo1: onCreate
 * ActivityDemo1: onStart
 * ActivityDemo1: onResume
 * ActivityDemo1: onPause
 * ActivityDemo1_2: onCreate
 * ActivityDemo1_2: onStart
 * ActivityDemo1_2: onResume
 * ActivityDemo1: onStop
 * ActivityDemo1_2: onPause
 * ActivityDemo1: onStart
 * ActivityDemo1: onResume
 * ActivityDemo1_2: onStop
 * ActivityDemo1_2: onDestroy
 *
 *
 * 注:关于如何通过 onSaveInstanceState() 和 onRestoreInstanceState() 来保存状态,请参见 /activity/ActivityDemo2.java
 */

package com.webabcd.androiddemo.activity;

import android.content.Intent;
import androidx.appcompat.app.AppCompatActivity;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.Button;

import com.webabcd.androiddemo.R;

public class ActivityDemo1 extends AppCompatActivity {

    private final String LOG_TAG = "ActivityDemo1";

    private Button mButton1;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        Log.d(LOG_TAG, "onCreate");

        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_activity_activitydemo1);

        mButton1 = findViewById(R.id.button1);
        mButton1.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Intent intent = new Intent(ActivityDemo1.this, ActivityDemo1_2.class);
                startActivity(intent);
            }
        });
    }

    @Override
    protected void onStart() {
        Log.d(LOG_TAG, "onStart");

        super.onStart();
    }

    @Override
    protected void onResume() {
        Log.d(LOG_TAG, "onResume");

        super.onResume();
    }

    @Override
    protected void onPause() {
        Log.d(LOG_TAG, "onPause");

        super.onPause();
    }

    @Override
    protected void onStop() {
        Log.d(LOG_TAG, "onStop");

        super.onStop();
    }

    @Override
    protected void onDestroy() {
        Log.d(LOG_TAG, "onDestroy");

        super.onDestroy();
    }

    // 用户按下了“返回”键,就会走到这里
    @Override
    public void onBackPressed() {
        Log.d(LOG_TAG, "onBackPressed");

        // 调用这句就走“返回”逻辑,不调用这句就阻止了“返回”
        super.onBackPressed();
    }

    // 用户离开了当前的 activity 就会走到这里(比如通过 startActivity() 离开,或者通过“home”键离开等)
    // 但是通过“返回”键离开,或者 finish() 离开则不会走到这里
    @Override
    protected void onUserLeaveHint() {
        Log.d(LOG_TAG, "onUserLeaveHint");

        super.onUserLeaveHint();
    }
}

\activity\ActivityDemo1_2.java

/**
 * Activity 的生命周期(参见 activity/ActivityDemo1 中的说明)
 */

package com.webabcd.androiddemo.activity;

import androidx.appcompat.app.AppCompatActivity;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.Button;

import com.webabcd.androiddemo.R;

public class ActivityDemo1_2 extends AppCompatActivity {

    private final String LOG_TAG = "ActivityDemo1_2";

    private Button mButton1;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        Log.d(LOG_TAG, "onCreate");

        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_activity_activitydemo1_2);

        mButton1 = findViewById(R.id.button1);
        mButton1.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                finish();
            }
        });
    }

    @Override
    protected void onStart() {
        Log.d(LOG_TAG, "onStart");

        super.onStart();
    }

    @Override
    protected void onResume() {
        Log.d(LOG_TAG, "onResume");

        super.onResume();
    }

    @Override
    protected void onPause() {
        Log.d(LOG_TAG, "onPause");

        super.onPause();
    }

    @Override
    protected void onStop() {
        Log.d(LOG_TAG, "onStop");

        super.onStop();
    }

    @Override
    protected void onDestroy() {
        Log.d(LOG_TAG, "onDestroy");

        super.onDestroy();
    }
}

/layout/activity_activity_activitydemo1.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical">

    <Button
        android:id="@+id/button1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:textAllCaps="false"
        android:text="启动另一个 activity"/>

    <ImageView
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:src="@drawable/img_activity_lifecycle"/>

</LinearLayout>

/layout/activity_activity_activitydemo1_2.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical">

    <Button
        android:id="@+id/button1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:textAllCaps="false"
        android:text="关闭"/>

</LinearLayout>

项目地址 https://github.com/webabcd/AndroidDemo
作者 webabcd

posted @ 2021-06-02 09:20  webabcd  阅读(365)  评论(0编辑  收藏  举报