我有 MainActivity.class n 我已经创建了弹出菜单并且有几个按钮我需要的是我需要将用户发送到我创建的新 Activity 。我的代码正在运行在 MainActivity.xml 上创建的按钮但是当我给弹出菜单按钮 ID 未启动我的应用程序。 期待支持。
package com.example.sampathmunaweera.mobilecw;
import android.content.Intent;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.widget.Button;
import android.view.View.OnClickListener;
import android.view.View;
import android.app.Activity;
import android.content.Context;
import android.view.Gravity;
import android.view.LayoutInflater;
import android.widget.PopupWindow;
import android.widget.RelativeLayout;
import android.view.ViewGroup.LayoutParams;
import android.widget.PopupMenu;
public class MainActivity extends AppCompatActivity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Button btnexit = (Button) findViewById(R.id.exit);
btnexit.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View v) {
// exit from app
finish();
System.exit(0);
}
});
// end exit function
final Button btnOpenPopup = (Button)findViewById(R.id.about);
btnOpenPopup.setOnClickListener(new OnClickListener(){
@Override
public void onClick(View arg0) {
LayoutInflater layoutInflater
= (LayoutInflater)getBaseContext()
.getSystemService(LAYOUT_INFLATER_SERVICE);
View popupView = layoutInflater.inflate(R.layout.popup_about, null);
final PopupWindow popupWindow = new PopupWindow(
popupView,
LayoutParams.WRAP_CONTENT,
LayoutParams.WRAP_CONTENT);
Button btnDismiss = (Button)popupView.findViewById(R.id.dismiss);
btnDismiss.setOnClickListener(new OnClickListener(){
@Override
public void onClick(View v) {
// TODO Auto-generated method stub
popupWindow.dismiss();
}});
//popupWindow.showAsDropDown(btnOpenPopup, 50, 50);
popupWindow.showAtLocation(btnOpenPopup, Gravity.CENTER, 0, 0);
}});
//pop up new game
final Button btnNewPopup = (Button)findViewById(R.id.newgame);
btnNewPopup.setOnClickListener(new OnClickListener(){
@Override
public void onClick(View arg0) {
LayoutInflater layoutInflater
= (LayoutInflater)getBaseContext()
.getSystemService(LAYOUT_INFLATER_SERVICE);
View popupView = layoutInflater.inflate(R.layout.popup_newgame, null);
final PopupWindow popupWindow = new PopupWindow(
popupView,
LayoutParams.WRAP_CONTENT,
LayoutParams.WRAP_CONTENT);
Button btnDismiss = (Button)popupView.findViewById(R.id.dismiss);
btnDismiss.setOnClickListener(new OnClickListener(){
@Override
public void onClick(View v) {
// TODO Auto-generated method stub
popupWindow.dismiss();
}});
//popupWindow.showAsDropDown(btnOpenPopup, 50, 50);
popupWindow.showAtLocation(btnOpenPopup, Gravity.CENTER, 0, 0);
}});
//open new activity
final Button btnNewNovise = (Button)findViewById(R.id.Novice);
btnNewNovise.setOnClickListener(new OnClickListener(){
@Override
public void onClick(View arg0) {
Intent myIntent = new Intent(MainActivity.this,
GameController.class);
startActivity(myIntent);
}});
}
public void openNewActivity (View view) {
}
}
弹出菜单xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:orientation="vertical"
android:background="@android:color/background_light">
<LinearLayout
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:orientation="vertical"
android:layout_margin="1dp"
android:background="@android:color/darker_gray">
>
<LinearLayout
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:orientation="vertical"
android:layout_margin="20dp">
<TextView
android:id="@+id/texttitle1"
android:textStyle="bold"
android:textSize="25dp"
android:textColor="#891800"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:text="Select Game Level" />
<Button
android:id="@+id/Novice"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:onClick="openNewActivity"
android:text="Novice" />
<Button
android:id="@+id/Easy"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:text="Easy" />
<Button
android:id="@+id/Hard"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:text="Hard" />
<Button
android:id="@+id/Guru"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:text="Guru" />
<Button
android:id="@+id/dismiss"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:text="Back to Menu" />
</LinearLayout>
</LinearLayout>
</LinearLayout>
Android list 代码
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.example.sampathmunaweera.mobilecw">
<application
android:allowBackup="true"
android:icon="@mipmap/ic_launcher"
android:label="@string/app_name"
android:supportsRtl="true"
android:installLocation="preferExternal"
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
android:label="@string/app_name"
android:name=".GameController"
android:windowSoftInputMode="stateHidden"></activity>
</application>
</manifest>
logcat 错误
03-06 14:19:20.982 4792-4792/com.example.sampathmunaweera.mobilecw E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.example.sampathmunaweera.mobilecw, PID: 4792
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.sampathmunaweera.mobilecw/com.example.sampathmunaweera.mobilecw.MainActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.Button.setOnClickListener(android.view.View$OnClickListener)' on a null object reference
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2325)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2387)
at android.app.ActivityThread.access$800(ActivityThread.java:151)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1303)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:135)
at android.app.ActivityThread.main(ActivityThread.java:5254)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:903)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:698)
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.Button.setOnClickListener(android.view.View$OnClickListener)' on a null object reference
at com.example.sampathmunaweera.mobilecw.MainActivity.onCreate(MainActivity.java:117)
at android.app.Activity.performCreate(Activity.java:5990)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1106)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2278)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2387)
at android.app.ActivityThread.access$800(ActivityThread.java:151)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1303)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:135)
at android.app.ActivityThread.main(ActivityThread.java:5254)
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:903)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:698)
最佳答案
可能会出错，但能够从弹出菜单 xml 中的按钮调用 GameController Activity :
<Button
android:id="@+id/Novice"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:onClick="openNewActivity"
android:text="Novice" />`
我刚刚添加了这些行:
public void openNewActivity (View view) {
if(view.getId()==R.id.Novice){
startActivity(new Intent(this,GameController.class));
}
}
在主要 Activity 中
关于java - 如何在 android studio 中使用弹出窗口按钮打开新 Activity ？，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/42620613/