在清单文件内添加activity-alias

<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/AppTheme">
        <activity android:name=".MainActivity">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />
                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
        <activity-alias
            android:name="RoundActivity"
            android:enabled="false"
            android:icon="@mipmap/launcher"
            android:targetActivity=".MainActivity">
            <intent-filter>
                <action android:name="android.intent.action.MAIN"/>
                <category android:name="android.intent.category.LAUNCHER"/>
            </intent-filter>
        </activity-alias>
        <activity-alias
            android:name="Round1Activity"
            android:enabled="false"
            android:icon="@mipmap/img1"
            android:targetActivity=".MainActivity">
            <intent-filter>
                <action android:name="android.intent.action.MAIN"/>
                <category android:name="android.intent.category.LAUNCHER"/>
            </intent-filter>
        </activity-alias>
    </application>

可添加多个activity-alias

name标签 任意起

enabled 要设置为false

icon 设置要改变的图标

targetActivity指向APP启动的activity

在MainActivity中加入

public class MainActivity extends AppCompatActivity {
    private Button btn1,btn2,btn3;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        btn1=findViewById(R.id.btn1);
        btn2=findViewById(R.id.btn2);
        btn3=findViewById(R.id.btn3);
        btn1.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                setPrimitiveIcon();
            }
        });
        btn2.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                setRoundIcon();
            }
        });
        btn3.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                setPrimitiveIcon2();
            }
        });
    }
    private void setPrimitiveIcon() {
        PackageManager packageManager = getPackageManager();
        packageManager.setComponentEnabledSetting(new ComponentName(this, getPackageName() +
                        ".RoundActivity"), PackageManager.COMPONENT_ENABLED_STATE_DISABLED,
                PackageManager.DONT_KILL_APP);
        packageManager.setComponentEnabledSetting(new ComponentName(this, getPackageName() +
                ".Round1Activity"), PackageManager.COMPONENT_ENABLED_STATE_DISABLED, PackageManager
                .DONT_KILL_APP);
        //设置默认图标
        packageManager.setComponentEnabledSetting(new ComponentName(this, getPackageName() +
                ".MainActivity"), PackageManager.COMPONENT_ENABLED_STATE_ENABLED, PackageManager
                .DONT_KILL_APP);
    }
    private void setRoundIcon() {
        PackageManager packageManager = getPackageManager();
        packageManager.setComponentEnabledSetting(new ComponentName(this, getPackageName() +
                ".MainActivity"), PackageManager.COMPONENT_ENABLED_STATE_DISABLED, PackageManager
                .DONT_KILL_APP);
        packageManager.setComponentEnabledSetting(new ComponentName(this, getPackageName() +
                ".Round1Activity"), PackageManager.COMPONENT_ENABLED_STATE_DISABLED, PackageManager
                .DONT_KILL_APP);
        //设置RoundActivity的图标
        packageManager.setComponentEnabledSetting(new ComponentName(this, getPackageName() +
                ".RoundActivity"), PackageManager.COMPONENT_ENABLED_STATE_ENABLED, PackageManager
                .DONT_KILL_APP);
    }
    private void setPrimitiveIcon2() {
        PackageManager packageManager = getPackageManager();
        packageManager.setComponentEnabledSetting(new ComponentName(this, getPackageName() +
                        ".MainActivity"), PackageManager.COMPONENT_ENABLED_STATE_DISABLED,
                PackageManager.DONT_KILL_APP);
        packageManager.setComponentEnabledSetting(new ComponentName(this, getPackageName() +
                ".RoundActivity"), PackageManager.COMPONENT_ENABLED_STATE_DISABLED, PackageManager
                .DONT_KILL_APP);
        //设置Round1Activity的图标
        packageManager.setComponentEnabledSetting(new ComponentName(this, getPackageName() +
                ".Round1Activity"), PackageManager.COMPONENT_ENABLED_STATE_ENABLED, PackageManager
                .DONT_KILL_APP);
    }

点击按钮后就会自动更换图标

注意：点击按钮后会有几秒的延迟然后更换图标，这个过程中点击图标会提示未安装此应用

此方法亲测有效