我正在开发一个应用程序，因为我想将控件从一个活动传递给另一个，并且我正在使用intent，如下所示，bt我在运行器中运行应用程序时遇到此类错误。不幸的是，app已经停止在android模拟器中显示由于：logcat中的java.lang.NullPointerException。 请告诉我这是什么问题以及该怎么做....？
JAVA file
import android.content.Context;
import android.support.v7.app.ActionBarActivity;
import android.os.Bundle;
import android.text.InputType;
import android.view.Menu;
import android.view.MenuItem;
import android.content.Intent;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;
import android.widget.Toast;
public class LifePartnerMainActivity extends ActionBarActivity {
EditText et1,et2;
Button b1,b2;
TextView tv1,tv2;
String lgid, pswd;
Context ctx;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_life_partner_main);
ctx=this;
et1=(EditText)findViewById(R.id.editText);
et2=(EditText)findViewById(R.id.editText2);
et2.setInputType(InputType.TYPE_CLASS_TEXT | InputType.TYPE_TEXT_VARIATION_PASSWORD);
tv1=(TextView)findViewById(R.id.textView);
tv2=(TextView)findViewById(R.id.textView2);
b1=(Button)findViewById(R.id.button);
b2=(Button)findViewById(R.id.button2);
b1.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
lgid=et1.getText().toString().trim();
pswd=et2.getText().toString().trim();
if(lgid.length()==0){
Toast.makeText(ctx, "Login ID should not be empty", Toast.LENGTH_LONG).show();
}else if(pswd.length()==0){
Toast.makeText(ctx, "Password should not be empty", Toast.LENGTH_LONG).show();
}else if(lgid.equals("admin")&&pswd.equals("1234")){
Intent in=new Intent(LifePartnerMainActivity.this,ShowList.class);
startActivity(in);
}else
Toast.makeText(ctx, "Login fails check your login credentials", Toast.LENGTH_LONG).show();
}
});
b2.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
Intent in=new Intent(LifePartnerMainActivity.this,Register.class);
startActivity(in);
}
});
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.menu_life_partner_main, menu);
return true;
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
// Handle action bar item clicks here. The action bar will
// automatically handle clicks on the Home/Up button, so long
// as you specify a parent activity in AndroidManifest.xml.
int id = item.getItemId();
//noinspection SimplifiableIfStatement
if (id == R.id.action_settings) {
return true;
}
return super.onOptionsItemSelected(item);
}
}
Manifest.xml File
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.nareshit.lifepartner" >
<application
android:allowBackup="true"
android:icon="@drawable/ic_launcher"
android:label="@string/app_name"
android:theme="@style/AppTheme" >
<activity
android:name=".LifePartnerMainActivity"
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:name=".Register"
android:label="@string/app_name" >
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.DEFAULT" />
</intent-filter>
</activity>
<activity android:name=".Filter"></activity>
<activity android:name=".MsgLog"></activity>
<activity android:name=".SendSMS"></activity>
<activity android:name=".ShowList"></activity>
<activity android:name=".TakePhoto"></activity>
</application>
</manifest>
Logcat Details:
02-05 09:52:55.973 2475-2475/com.nareshit.lifepartner W/dalvikvm﹕ threadid=1: thread exiting with uncaught exception (group=0xb4ded908)
02-05 09:52:56.062 2475-2475/com.nareshit.lifepartner E/AndroidRuntime﹕ FATAL EXCEPTION: main
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.nareshit.lifepartner/com.nareshit.lifepartner.ShowList}: java.lang.NullPointerException
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2180)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2230)
at android.app.ActivityThread.access$600(ActivityThread.java:141)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1234)
at android.os.Handler.dispatchMessage(Handler.java:99)
at android.os.Looper.loop(Looper.java:137)
at android.app.ActivityThread.main(ActivityThread.java:5039)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:511)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560)
at dalvik.system.NativeStart.main(Native Method)
Caused by: java.lang.NullPointerException
at com.nareshit.lifepartner.ShowList.onCreate(ShowList.java:29)
at android.app.Activity.performCreate(Activity.java:5104)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1080)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2144)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2230)
at android.app.ActivityThread.access$600(ActivityThread.java:141)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1234)
at android.os.Handler.dispatchMessage(Handler.java:99)
at android.os.Looper.loop(Looper.java:137)
at android.app.ActivityThread.main(ActivityThread.java:5039)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:511)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560)
at dalvik.system.NativeStart.main(Native Method)
答案 0 :(得分：0)
问题似乎与您的ShowList文件有关。
由于您尚未发布ShowList文件的内容，我猜可能您正试图利用某些视图而不会在任何地方声明。
如果您使用的是 NullPointerException ，也可以返回调用findViewById时错误的上下文。例如，您可能正在尝试访问对话框中的按钮，仍然使用findViewById而不是dialog.findViewById（其中'对话'是对话框的实例）。
我希望你了解这个问题。如果您需要更多帮助，您也可以发布您的ShowList代码。