Java.lang.ClassCastException：无法将android.widget.RelativeLayout强制转换为android.widget.FrameLayout

Question

I try to create unity Subview for my android app. But I got a error like this

 E/AndroidRuntime(1750): Caused by: java.lang.RuntimeException: Unable to start activity ComponentInfo{com.duy/com.duy.MainActivity}: java.lang.ClassCastException: android.widget.RelativeLayout cannot be cast to android.widget.FrameLayout

This is my Java code

package com.duy;

import android.app.Activity;
import android.os.Bundle;
import android.view.View;
import android.widget.FrameLayout;
import android.widget.LinearLayout.LayoutParams;

import com.unity3d.player.UnityPlayer;


public class MainActivity extends Activity {

    private UnityPlayer m_UnityPlayer;

    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        // Create the UnityPlayer
        m_UnityPlayer = new UnityPlayer(this);
        int glesMode = m_UnityPlayer.getSettings().getInt("gles_mode", 1);
        boolean trueColor8888 = false;
        m_UnityPlayer.init(glesMode, trueColor8888);

        setContentView(R.layout.main);

        // Add the Unity view
        FrameLayout layout = (FrameLayout) findViewById(R.id.frameLayout2);    
        LayoutParams lp = new LayoutParams (LayoutParams.FILL_PARENT, LayoutParams.FILL_PARENT);
        layout.addView(m_UnityPlayer.getView(), 0, lp);
    }
}

and this is my xml file:

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:id="@+id/frameLayout2"
android:layout_width="fill_parent"
android:layout_height="fill_parent" >

</RelativeLayout>

And I got the following error:

06-24 09:20:41.680: E/AndroidRuntime(1913): FATAL EXCEPTION: main
06-24 09:20:41.680: E/AndroidRuntime(1913): Process: com.duy, PID: 1913
06-24 09:20:41.680: E/AndroidRuntime(1913): java.lang.Error: FATAL EXCEPTION [main]
06-24 09:20:41.680: E/AndroidRuntime(1913): Unity version     : 5.1.1f1
06-24 09:20:41.680: E/AndroidRuntime(1913): Device model      : unknown Android SDK built for x86
06-24 09:20:41.680: E/AndroidRuntime(1913): Device fingerprint: generic_x86/sdk_x86/generic_x86:4.4.2/KK/999428:eng/test-keys
06-24 09:20:41.680: E/AndroidRuntime(1913): Caused by: java.lang.RuntimeException: Unable to start activity ComponentInfo{com.duy/com.duy.MainActivity}: java.lang.ClassCastException: android.widget.RelativeLayout cannot be cast to android.widget.FrameLayout
06-24 09:20:41.680: E/AndroidRuntime(1913):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2195)
06-24 09:20:41.680: E/AndroidRuntime(1913):     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2245)
06-24 09:20:41.680: E/AndroidRuntime(1913):     at android.app.ActivityThread.access$800(ActivityThread.java:135)
06-24 09:20:41.680: E/AndroidRuntime(1913):     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1196)
06-24 09:20:41.680: E/AndroidRuntime(1913):     at android.os.Handler.dispatchMessage(Handler.java:102)
06-24 09:20:41.680: E/AndroidRuntime(1913):     at android.os.Looper.loop(Looper.java:136)
06-24 09:20:41.680: E/AndroidRuntime(1913):     at android.app.ActivityThread.main(ActivityThread.java:5017)
06-24 09:20:41.680: E/AndroidRuntime(1913):     at java.lang.reflect.Method.invokeNative(Native Method)
06-24 09:20:41.680: E/AndroidRuntime(1913):     at java.lang.reflect.Method.invoke(Method.java:515)
06-24 09:20:41.680: E/AndroidRuntime(1913):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:779)
06-24 09:20:41.680: E/AndroidRuntime(1913):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:595)
06-24 09:20:41.680: E/AndroidRuntime(1913):     at dalvik.system.NativeStart.main(Native Method)
06-24 09:20:41.680: E/AndroidRuntime(1913): Caused by: java.lang.ClassCastException: android.widget.RelativeLayout cannot be cast to android.widget.FrameLayout
06-24 09:20:41.680: E/AndroidRuntime(1913):     at com.duy.MainActivity.onCreate(MainActivity.java:30)
06-24 09:20:41.680: E/AndroidRuntime(1913):     at android.app.Activity.performCreate(Activity.java:5231)
06-24 09:20:41.680: E/AndroidRuntime(1913):     at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1087)
06-24 09:20:41.680: E/AndroidRuntime(1913):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2159)
06-24 09:20:41.680: E/AndroidRuntime(1913):     ... 11 more

How can I solve this problem ?

Answer 1

R.id.frameLayout2 is NOT a frame layout. Look at your XML again.

That means the line: FrameLayout layout = (FrameLayout) findViewById(R.id.frameLayout2); is wrong, so you have a ClassCastException

But if all you want is to have the unity player view, you can use just that:

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);

    // Create the UnityPlayer
    m_UnityPlayer = new UnityPlayer(this);
    int glesMode = m_UnityPlayer.getSettings().getInt("gles_mode", 1);
    boolean trueColor8888 = false;
    m_UnityPlayer.init(glesMode, trueColor8888);

    setContentView(m_UnityPlayer.getView());
}

Answer 2

Basically you have tried to cast a Framelayout to a Relativelayout, in your xml you can see it is a relativelayout:

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:id="@+id/frameLayout2"
android:layout_width="fill_parent"
android:layout_height="fill_parent" >

</RelativeLayout><!--Notice it says Relativelayout-->

You can't do this:

FrameLayout layout = (FrameLayout) findViewById(R.id.frameLayout2);

Because it is actually a Relativelayout, not a Framelayout, even though you called it 'framelayout2' it is still a Relativelayout.

I recommend this one as you end up with a framelayout and that follows your tutorial more accurately. Change the Relativelayout in the XML file into a framelayout, it's very simple:

New XML File:

<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:id="@+id/frameLayout2"
android:layout_width="fill_parent"
android:layout_height="fill_parent" >

</FrameLayout><!--Notice it says FrameLayout Now.-->

This will completely solve your problem, with no extra steps.

You could also change the code in you Java to reflect that it is a relativelayout, however this doesn't follow your tutorial as much but it's good to know.

New Java:

RelativeLayout layout = (RelativeLayout) findViewById(R.id.framelayout2);

That should also work, but again that makes it a relativelayout no a framelayout so it might mess up your tutorial.