Android jumps from one App interface to another App interface

Android jumps from one App interface to another App interface
First, expose the activity of the App that needs to be jumped

 <activity
        android:name=".MainPage"
        android:exported="true">
    </activity>

It should be noted that if it is not exposed, an error will be reported

Then write the following code at the place where the jump is required
to display Start
1 Common

  Intent intent =new Intent(FirstActivity.this,SecondActivity.class);
        startActivity(intent);

2 ComponentName via Intent:

//前提：知道要跳转应用的包名、类名
Intent intent =new Intent(Intent.ACTION_MAIN);
//ComponentName的第一处是package的包名，第二个是锁需要进行跳转的类名
ComponentName componentName = new 
ComponentName("com.example.selftest","com.example.selftest.MainPage");
intent.setComponent(componentName);
startActivity(intent);

3 Specify the package name when initializing the Intent:

Intent intent = new Intent("android.intent.action.MAIN");
intent.setClassName("当前Act的全限定类名","启动Act的全限定类名");
startActivity(intent);

Implicit start
is realized through Action, Category or data of Intent-filter

Intent intent1 =new Intent("com.example.helloandroid.core.action.SecondActivity");
                startActivity(intent1);