当我按下按钮调用 function 时，我的应用程序崩溃了

Question

I am trying to make a simple gallery app. When I try this code:

public void previousTap(View view){
    ImageView img = (ImageView) view;
    if (img.getTag() == "img_one") {
        img.setImageResource(R.drawable.img_five);
        img.setTag("img_five");
    } else if (img.getTag() == "img_two") {
        img.setImageResource(R.drawable.img_one);
        img.setTag("img_one");
    } else if (img.getTag() == "img_three") {
        img.setImageResource(R.drawable.img_two);
        img.setTag("img_two");
    } else if (img.getTag() == "img_four") {
        img.setImageResource(R.drawable.img_three);
        img.setTag("img_three");
    } else if (img.getTag() == "img_five") {
        img.setImageResource(R.drawable.img_four);
        img.setTag("img_four");
    }
}

When I run my project and install the app and click on the previous button, my app crashes. Why? Also, is there any way to get the tag of an imageview in activity_main.xml rather than typing "ImageView img = (ImageView) view;"(Only if it is wrong)?

The error I get:

E/AndroidRuntime: FATAL EXCEPTION: main
    Process: com.wali.photoframegallery, PID: 6166
    java.lang.IllegalStateException: Could not execute method for android:onClick
        at androidx.appcompat.app.AppCompatViewInflater$DeclaredOnClickListener.onClick(AppCompatViewInflater.java:402)
        at android.view.View.performClick(View.java:6603)
        at android.view.View.performClickInternal(View.java:6576)
        at android.view.View.access$3100(View.java:780)
        at android.view.View$PerformClick.run(View.java:26090)
        at android.os.Handler.handleCallback(Handler.java:873)
        at android.os.Handler.dispatchMessage(Handler.java:99)
        at android.os.Looper.loop(Looper.java:235)
        at android.app.ActivityThread.main(ActivityThread.java:6760)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:493)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:911)
     Caused by: java.lang.reflect.InvocationTargetException
        at java.lang.reflect.Method.invoke(Native Method)
        at androidx.appcompat.app.AppCompatViewInflater$DeclaredOnClickListener.onClick(AppCompatViewInflater.java:397)
        at android.view.View.performClick(View.java:6603) 
        at android.view.View.performClickInternal(View.java:6576) 
        at android.view.View.access$3100(View.java:780) 
        at android.view.View$PerformClick.run(View.java:26090) 
        at android.os.Handler.handleCallback(Handler.java:873) 
        at android.os.Handler.dispatchMessage(Handler.java:99) 
        at android.os.Looper.loop(Looper.java:235) 
        at android.app.ActivityThread.main(ActivityThread.java:6760) 
        at java.lang.reflect.Method.invoke(Native Method) 
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:493) 
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:911) 
     Caused by: java.lang.ClassCastException: androidx.appcompat.widget.AppCompatButton cannot be cast to android.widget.ImageView
        at com.wali.photoframegallery.MainActivity.nextTap(MainActivity.java:32)
        at java.lang.reflect.Method.invoke(Native Method) 
        at androidx.appcompat.app.AppCompatViewInflater$DeclaredOnClickListener.onClick(AppCompatViewInflater.java:397) 
        at android.view.View.performClick(View.java:6603) 
        at android.view.View.performClickInternal(View.java:6576) 
        at android.view.View.access$3100(View.java:780) 
        at android.view.View$PerformClick.run(View.java:26090) 
        at android.os.Handler.handleCallback(Handler.java:873) 
        at android.os.Handler.dispatchMessage(Handler.java:99) 
        at android.os.Looper.loop(Looper.java:235) 
        at android.app.ActivityThread.main(ActivityThread.java:6760) 
        at java.lang.reflect.Method.invoke(Native Method) 
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:493) 
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:911)

EDIT: I tried changing this:

ImageView img = (ImageView) view;

To this:

View img = (View) view;

It gave me no errors, but there is no more functionality. What's wrong now?

Answer 1

You can see your problem in next line: Caused by: java.lang.ClassCastException: androidx.appcompat.widget.AppCompatButton cannot be cast to android.widget.ImageView of your stack trace. You can try to cast view in AppCompatButton, or change AppCompatButton to ImageView in your layout