我是一名初學android程序員。我正在學習溢出菜單的概念,通過製作一個應用程序來改變背景顏色,當菜單中的三項之一被選中時。我不明白爲什麼我的應用程序從選項中選擇一個項目後關閉,並顯示以上錯誤。不幸的<app>已停止工作(溢出菜單)
這裏是我的MainActivity.java文件
package com.awani.overflowmenu;
import android.graphics.Color;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.widget.RelativeLayout;
import android.view.View;
import android.view.Menu;
import android.view.MenuItem;
public class MainActivity extends AppCompatActivity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
}
@Override
public boolean onCreateOptionsMenu(Menu menu){
getMenuInflater().inflate(R.menu.main_menu,menu);
// return super.onCreateOptionsMenu(menu);
return true;
}
@Override
public boolean onOptionsItemSelected(MenuItem item){
RelativeLayout main_view = (RelativeLayout) findViewById(R.id.main_view);
//test which item is selected by user
switch (item.getItemId()){
case R.id.menu_red:
if(item.isChecked())
item.setChecked(false);
else
item.setChecked(true);
main_view.setBackgroundColor(Color.RED);
return true;
case R.id.menu_green:
if(item.isChecked())
item.setChecked(false);
else
item.setChecked(true);
main_view.setBackgroundColor(Color.GREEN);
return true;
case R.id.menu_yellow:
if(item.isChecked())
item.setChecked(false);
else
item.setChecked(true);
main_view.setBackgroundColor(Color.YELLOW);
return true;
default:
return super.onOptionsItemSelected(item);
}
}
}
在MainActivity.java
,在onOptionsItemSelected(菜單菜單)功能,我的(RelativeLayout的)findviewbyid下獲得紅線(R.id.main_view) .it說'意外投到RelativeLayout.but gradle已成功構建。
我看到其他的答案,但不能涉及到我的情況
事件日誌中這樣說:
FATAL EXCEPTION: main
Process:com.awani.overflowmenu, PID: 26829
java.lang.ClassCastException: android.support.v7.widget.AppCompatTextView cannot be cast to android.widget.RelativeLayout
at com.awani.overflowmenu.MainActivity.onOptionsItemSelected(MainActivity.java:30)
at android.app.Activity.onMenuItemSelected(Activity.java:3201)
at android.support.v4.app.FragmentActivity.onMenuItemSelected(FragmentActivity.java:408)
at android.support.v7.app.AppCompatActivity.onMenuItemSelected(AppCompatActivity.java:195)
at android.support.v7.view.WindowCallbackWrapper.onMenuItemSelected(WindowCallbackWrapper.java:113)
at android.support.v7.app.AppCompatDelegateImplV9.onMenuItemSelected(AppCompatDelegateImplV9.java:679)
at android.support.v7.view.menu.MenuBuilder.dispatchMenuItemSelected(MenuBuilder.java:822)
at android.support.v7.view.menu.MenuItemImpl.invoke(MenuItemImpl.java:156)
at android.support.v7.view.menu.MenuBuilder.performItemAction(MenuBuilder.java:969)
at android.support.v7.view.menu.MenuPopup.onItemClick(MenuPopup.java:127)
at android.widget.AdapterView.performItemClick(AdapterView.java:340)
at android.widget.AbsListView.performItemClick(AbsListView.java:1530)
at android.widget.AbsListView$PerformClick.run(AbsListView.java:3698)
at android.widget.AbsListView$3.run(AbsListView.java:5682)
at android.os.Handler.handleCallback(Handler.java:739)
at android.os.Handler.dispatchMessage(Handler.java:95)
at android.os.Looper.loop(Looper.java:145)
at android.app.ActivityThread.main(ActivityThread.java:6917)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1404)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1199)
可以張貼主要活動你的XML佈局? – mdb
異常是「android.support.v7.widget.AppCompatTextView不能轉換爲android.widget.RelativeLayout」,你的代碼是(RelativeLayout)findViewById(R.id.main_view);'(至少你已經發布了什麼這裏),但你不明白該怎麼辦? – Tom
檢查你的xml視圖id(R.id.main_view) –