android学习记录(二)「这是我参与11月更文挑战的第11天，活动详情查看：2021最后一次更文挑战」模拟Acti

「这是我参与11月更文挑战的第11天，活动详情查看：2021最后一次更文挑战」

模拟Activity的生命周期

在这里插入图片描述 Activity有7个状态. 为了模拟这七个状态.创建三个Activity

MainActivity

package com.example.activityrecycletest;

import androidx.appcompat.app.AppCompatActivity;

import android.content.Intent;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.Button;
public class MainActivity extends AppCompatActivity {
    private Button button01;
    private Button button02;
    String string="MainActivity";
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        initView();
        Log.d(string,"onCreate");//通过日志来记录这七个状态的运行情况.

    }

    @Override
    protected void onStart() {
        super.onStart();
        Log.d(string,"onStart");
    }

    @Override
    protected void onResume() {
        super.onResume();
        Log.d(string,"onResume");
    }

    @Override
    protected void onPause() {
        super.onPause();
        Log.d(string,"onPause");
    }

    @Override
    protected void onStop() {
        super.onStop();
        Log.d(string,"onStop");
    }

    @Override
    protected void onDestroy() {
        super.onDestroy();
        Log.d(string,"onDestroy");
    }

    @Override
    protected void onRestart() {
        super.onRestart();
        Log.d(string,"onRestart");
    }

    public void initView(){
        button01=findViewById(R.id.btn_start_normal_activity);
        button02=findViewById(R.id.btn_start_DialogActivity);
        button01.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Intent intent=new Intent(MainActivity.this,NormalActivity.class);
                startActivity(intent);
            }
        });
        button02.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Intent intent=new Intent(MainActivity.this,DialogActivity.class);
                startActivity(intent);
            }
        });


    }
}

NormalActivity

package com.example.activityrecycletest;

import androidx.appcompat.app.AppCompatActivity;

import android.os.Bundle;

public class NormalActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_normal);
    }
}

DialogActivity

package com.example.activityrecycletest;

import androidx.appcompat.app.AppCompatActivity;

import android.os.Bundle;

public class DialogActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_dialog);
    }
}

启动App后在这里插入图片描述调用了三个方法.此时MainActivity 处于onResume 点击startNormalActivity后 MainActivity 停止了. 点击返回后重新启动了. 点击 startDialogActivity后 MainActivity 处于暂停状态. 点击返回后又处于onResume状态. 退出应用后 MainActivity被销毁.

Activity的四种启动模式

standard 标准模式

每次启动Activity 会在当前的任务栈中创建一个新的实例.

FirstActivity.java

package com.example.launchmodetest;

import androidx.appcompat.app.AppCompatActivity;

import android.content.Intent;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.Button;

public class FirstActivity extends AppCompatActivity {
    private Button button01;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        Log.d("FirstActivity",this.toString());//打印实例
        initView();
    }
    public void initView(){
        button01=findViewById(R.id.button01);
        button01.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Intent intent=new Intent(FirstActivity.this,FirstActivity.class);
                startActivity(intent);
            }
        });

    }
}

在这里插入图片描述点击button01后发现两次不同

singleTop模式

如果新创建的Activity位于栈顶,那么不会创建.

FirstActivity.java

package com.example.launchmodetest;

import androidx.appcompat.app.AppCompatActivity;

import android.content.Intent;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.Button;

public class FirstActivity extends AppCompatActivity {
    private Button button01;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        initView();
    }

    @Override
    protected void onResume() {
        super.onResume();
        Log.d("FirstActivity",this.toString());
    }


    public void initView(){
        button01=findViewById(R.id.button01);
        button01.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Intent intent=new Intent(FirstActivity.this,FirstActivity.class);
                startActivity(intent);
            }
        });
    }
}

结果在这里插入图片描述发现当活动处于栈顶时,不会创建新的Activity

当活动不处于栈顶时

FirstActivity.java

package com.example.launchmodetest;

import androidx.appcompat.app.AppCompatActivity;

import android.content.Intent;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.Button;

public class FirstActivity extends AppCompatActivity {
    private Button button01;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        initView();
    }

    @Override
    protected void onResume() {
        super.onResume();
        Log.d("FirstActivity",this.toString());
    }


    public void initView(){
        button01=findViewById(R.id.button01);
        button01.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Intent intent=new Intent(FirstActivity.this,SecondActivity.class);
                startActivity(intent);
            }
        });
    }
}

SecondActivity.java

package com.example.launchmodetest;

import androidx.appcompat.app.AppCompatActivity;

import android.content.Intent;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;

public class SecondActivity extends AppCompatActivity {
    private Button button2;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_second);
        initView();
    }
    public  void initView(){
        button2=findViewById(R.id.button02);
        button2.setOnClickListener(new View.OnClickListener(){
            @Override
            public void onClick(View v) {
                Intent intent =new Intent(SecondActivity.this,FirstActivity.class);
                startActivity(intent);
            }
        });

    }
}

此时的运行结果在这里插入图片描述发现当不处于栈顶时,会创建新的活动实例.

singleTask模式

和singleTop不同的是,只要任务栈中存在Activity的实例,就会调用该实例,将该实例上面的Activity出栈. 在AndroidManifest.xml中将singleTop修改成singleTask

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.example.launchmodetest">
    <application
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:roundIcon="@mipmap/ic_launcher_round"
        android:supportsRtl="true"
        android:theme="@style/Theme.LaunchModeTest">
        <activity android:name=".SecondActivity"></activity>
        <activity
            android:name=".FirstActivity"
            android:launchMode="singleTask">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
    </application>
</manifest>

重新运行. 在这里插入图片描述发现打印出的是相同的实例.

singleInstance模式

具有此模式的Activity只能单独位于一个任务栈中，且此任务栈中只有唯一一个实例。

添加一个ThirdActivity

package com.example.launchmodetest;

import androidx.appcompat.app.AppCompatActivity;

import android.os.Bundle;
import android.util.Log;

public class ThirdActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_third);
    }
    protected void onResume() {
        super.onResume();
        Log.d("ThirdActivity",""+getTaskId());
    }
}

AndroidManifest.xml

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.example.launchmodetest">

    <application
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:roundIcon="@mipmap/ic_launcher_round"
        android:supportsRtl="true"
        android:theme="@style/Theme.LaunchModeTest">
        <activity android:name=".ThirdActivity"></activity>
        <activity
            android:name=".SecondActivity"
            android:launchMode="singleInstance" />
        <activity android:name=".FirstActivity">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
    </application>

</manifest>

运行结果在这里插入图片描述可以发现FirstActivity和ThirdActivity得任务栈相同.而SecondActivity不同.