我正在使用 android 2.2 和 eclipse 制作一个 android 应用程序。
应用程序有两个工作流程:
WF1: CoverPageApp -> LoginActivity -> Dashboard。
WF2: CoverPageApp -> RegisterActivity -> Dashboard。
但是当我单击 CoverPageApp 中的“开始”按钮继续另一个 Activity (即 LoginActivity)时，应用程序强制关闭。
我还包含了显示 Null Exception 错误的 LogCat，并且在 LoginActivity Java 文件中它指向第 51 行:
btnLinkToRegistrScrn =(按钮)findViewById(R.id.LinkToRegisterScreen);
AndroidManifest.xml
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.app.android"
android:versionCode="1"
android:versionName="1.0" >
<uses-sdk android:targetSdkVersion="15" android:minSdkVersion="8" />
<uses-permission android:name="android.permission.ACCESS_FINE_LOCATION" />
<uses-permission android:name="android.permission.INTERNET" />
<application
android:icon="@drawable/ic_launcher"
android:label="@string/app_name" >
<activity
android:enabled="true"
android:name=".PageApp"
android:label="@string/app_name" >
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
<activity
android:enabled="true"
android:name=".LoginActivity1"
android:label="Login Activity" >
</activity>
<activity
android:enabled="true"
android:name=".CAActivity"
android:label="Register Activity" >
</activity>
<activity
android:enabled="true"
android:name=".DashboardActivity"
android:label="Dashboard Activity" >
</activity>
</application>
</manifest>
PageApp.java
import android.app.Activity;
import android.os.Bundle;
//import android.content.Context;
import android.content.Intent;
import android.widget.Button;
import android.view.View;
public class PageApp extends Activity {
Button startbutton;
/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.coverpage);
addListenerOnButton();
}
public void addListenerOnButton() {
//final Context context1 = this;
startbutton = (Button) findViewById(R.id.button1);
startbutton.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View arg0) {
Intent intent1 = new Intent(arg0.getContext(), LoginActivity1.class);
// intent1.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
startActivity(intent1);
finish();
}
});
}
}
Log.java
import android.app.Activity;
//import android.content.Context;
import android.content.Intent;
import android.os.Bundle;
import android.view.View;
//import android.view.View.OnClickListener;
import android.widget.Button;
//import android.widget.TextView;
public class Log extends Activity {
Button btnLinkToRegistrScrn;
Button loginbtn1;
/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.login);
addListenerOnButton();
// btnLinkToRegistrScrn = (Button) findViewById(R.id.LinkToRegisterScreen);
}
public void addListenerOnButton() {
//final Context context2 = this;
loginbtn1 = (Button) findViewById(R.id.btnLogin);
loginbtn1.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View arg0) {
Intent intent = new Intent(arg0.getContext(), DashboardActivity.class);
intent.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
startActivity(intent);
}
});
}
{
// Link to Register Screen
btnLinkToRegistrScrn = (Button) findViewById(R.id.LinkToRegisterScreen);
btnLinkToRegistrScrn.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
Intent i = new Intent(v.getContext(), CAaactivity.class);
// i.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
startActivity(i);
}
});
}
}
LOGCAT
05-31 17:53:19.691: D/AndroidRuntime(1958): Shutting down VM
05-31 17:53:19.710: W/dalvikvm(1958): threadid=1: thread exiting with uncaught exception (group=0x4001d800)
05-31 17:53:19.730: E/AndroidRuntime(1958): FATAL EXCEPTION: main
05-31 17:53:19.730: E/AndroidRuntime(1958): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2585)
05-31 17:53:19.730: E/AndroidRuntime(1958): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2679)
05-31 17:53:19.730: E/AndroidRuntime(1958): at android.app.ActivityThread.access$2300(ActivityThread.java:125)
05-31 17:53:19.730: E/AndroidRuntime(1958): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2033)
05-31 17:53:19.730: E/AndroidRuntime(1958): at android.os.Handler.dispatchMessage(Handler.java:99)
05-31 17:53:19.730: E/AndroidRuntime(1958): at android.os.Looper.loop(Looper.java:123)
05-31 17:53:19.730: E/AndroidRuntime(1958): at android.app.ActivityThread.main(ActivityThread.java:4627)
05-31 17:53:19.730: E/AndroidRuntime(1958): at java.lang.reflect.Method.invokeNative(Native Method)
05-31 17:53:19.730: E/AndroidRuntime(1958): at java.lang.reflect.Method.invoke(Method.java:521)
05-31 17:53:19.730: E/AndroidRuntime(1958): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:868)
05-31 17:53:19.730: E/AndroidRuntime(1958): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:626)
05-31 17:53:19.730: E/AndroidRuntime(1958): at dalvik.system.NativeStart.main(Native Method)
05-31 17:53:19.730: E/AndroidRuntime(1958): Caused by: java.lang.NullPointerException
05-31 17:53:19.730: E/AndroidRuntime(1958): at android.app.Activity.findViewById\untime(1958): at java.lang.Class.newInstanceImpl(Native Method)
05-31 17:53:19.730: E/AndroidRuntime(1958): at java.lang.Class.newInstance(Class.java:1429)
05-31 17:53:19.730: E/AndroidRuntime(1958): at android.app.Instrumentation.newActivity(Instrumentation.java:1021)
05-31 17:53:19.730: E/AndroidRuntime(1958): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2577)
05-31 17:53:19.730: E/AndroidRuntime(1958): ... 11 more
最佳答案
在您声明的 Login.xml 中
<TextView
android:id="@+id/LinkToRegisterScreen"
android:layout_width="fill_parent"
android:layout_height="wrap_content"/>
同时映射 LoginActivity1.java
btnLinkToRegistrScrn = (Button) findViewById(R.id.LinkToRegisterScreen);
所以只需将 TextView 更改为 Button
<Button
android:id="@+id/LinkToRegisterScreen"
android:layout_width="fill_parent"
android:layout_height="wrap_content"/>
关于java - Android 应用程序在进行另一项 Activity 时强制关闭，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/10892398/