Activity的四种启动方式Demo和总结

1、activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/activity_main"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    tools:context="example.com.myapplication.MainActivity">

    <Button
        android:text="second"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_marginTop="27dp"
        android:id="@+id/button"
        android:onClick="secondActivty"
        android:visibility="visible"
        android:layout_alignParentStart="true" />

    <Button
        android:text="first"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_below="@+id/button"
        android:layout_alignParentStart="true"
        android:layout_marginTop="13dp"
        android:id="@+id/button2"
        android:onClick="firstyActivty"
        android:visibility="visible" />

</RelativeLayout>

2、MainActivity.java

package example.com.myapplication;

import android.app.Activity;
import android.content.Intent;
import android.content.pm.ActivityInfo;
import android.content.pm.PackageManager;
import android.os.Bundle;
import android.util.Log;
import android.view.View;

public class MainActivity extends Activity {
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        try {
            ActivityInfo info = this.getPackageManager().getActivityInfo(getComponentName(), 0);
            Log.i("xxxxx", "taskId:" + getTaskId() + ";  activityInfo:" + info.toString() + "\n");

        } catch (PackageManager.NameNotFoundException e) {

        }
    }

    public void secondActivty(View v) {
        Intent intent = new Intent(MainActivity.this, SecondActivity.class);
        startActivity(intent);
    }


    public void firstyActivty(View v) {
        Intent intent = new Intent(MainActivity.this, MainActivity.class);
        startActivity(intent);
    }


}

3、activity_second.xml

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/activity_second"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    tools:context="example.com.myapplication.SecondActivity">

    <Button
        android:text="third"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_alignParentTop="true"
        android:layout_alignParentStart="true"
        android:id="@+id/button2"
        android:visibility="visible"
        android:onClick="thirdActivity" />

    <Button
        android:text="first"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_alignParentStart="true"
        android:layout_marginTop="33dp"
        android:id="@+id/button5"
        android:visibility="visible"
        android:onClick="startFistActivity" />
</RelativeLayout>

4、SecondActivity.java

package example.com.myapplication;

import android.app.Activity;
import android.content.Intent;
import android.content.pm.ActivityInfo;
import android.content.pm.PackageManager;
import android.os.Bundle;
import android.util.Log;
import android.view.View;

public class SecondActivity extends Activity {
    /*TextView txv, txv2;
    ActivityInfo info;*/

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_second);
        /*txv = findViewById(R.id.textView3);
        txv2 = findViewById(R.id.textView4);*/

        try {
            ActivityInfo info = this.getPackageManager().getActivityInfo(getComponentName(), 0);
            Log.i("xxxxxx", "taskId:" + getTaskId() + ";  activityInfo:" + info.toString());
        } catch (PackageManager.NameNotFoundException e) {

        }
        /*txv.setText(String.valueOf(taskId));
        txv2.setText(info.toString());*/
    }

    public void thirdActivity(View v) {
        Intent intent = new Intent(this, SecondActivity.class);
        startActivity(intent);
    }

    public void startFistActivity(View v) {
        Intent intent = new Intent(this, MainActivity.class);
        startActivity(intent);
    }
}

5、AndroidManifest.xml

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="example.com.myapplication">
    <!--
    android:launchMode="singleInstance"
    android:launchMode="singleTask"
    android:launchMode="singleTop"
    android:launchMode="standard"
    -->

    <application
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:supportsRtl="true"
        android:theme="@style/AppTheme">
        <activity android:name=".MainActivity"
            android:launchMode="standard"
            >
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
        <activity
            android:name=".SecondActivity"
            android:label="@string/title_activity_second" />
    </application>

</manifest>

总结