Eclipse：错误java.lang.NullPointerException

吉尔·星期五·马塞洛

当我在上输入信息时，会发生这种情况popupWindow。

Java代码：

package com.example.istronggyminstructor;

import android.os.Bundle;
import android.app.Activity;
import android.content.Intent;
import android.database.Cursor;
import android.view.Gravity;
import android.view.LayoutInflater;
import android.view.Menu;
import android.view.View;
import android.view.View.OnClickListener;
import android.view.ViewGroup;
import android.view.ViewGroup.LayoutParams;
import android.view.WindowManager;
import android.widget.Button;
import android.widget.EditText;
import android.widget.FrameLayout;
import android.widget.PopupWindow;
import android.widget.TextView;
import android.widget.Toast;

public class CurrentUsers extends Activity {
private Button register;
private Button adduser;
EditText getusertext, getpass, getweight, textdisp;
DBAdapter myDB;



protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_current_users);
    register = (Button)findViewById(R.id.regbut);
    adduser = (Button)findViewById(R.id.addbut);
    register.setOnClickListener(new OnClickListener(){
        @Override
        public void onClick(View arg0) {
            LayoutInflater inflator=(LayoutInflater)getBaseContext().getSystemService(LAYOUT_INFLATER_SERVICE);
            View popupview=inflator.inflate(R.layout.popup, null);
            final PopupWindow popupWindow = new PopupWindow(popupview, LayoutParams.WRAP_CONTENT,LayoutParams.WRAP_CONTENT);
            popupWindow.showAtLocation(popupview, Gravity.CENTER, 0, 0);
            popupWindow.setFocusable(true);
            popupWindow.update();
            Button dismissbtn = (Button)popupview.findViewById(R.id.close);
            dismissbtn.setOnClickListener(new OnClickListener(){
                @Override
                public void onClick(View arg0) {
                    popupWindow.dismiss();
                }
            });
            popupWindow.showAsDropDown(register, 50, -30);
        }
    });
    openDB();

}
public void openDB(){
    myDB = new DBAdapter(this);
    myDB.open();
}

private void closeDB() {
    myDB.close();
}

private void displayText(String message) {
    TextView textView = (TextView) findViewById(R.id.textdisp);
    textView.setText(message);
}

public void registerUser(View v) {
    EditText username = (EditText)findViewById(R.id.usertext);
    EditText password = (EditText)findViewById(R.id.passwordtext);
    EditText weight = (EditText)findViewById(R.id.weight);
    String getUsername = username.getText().toString();
    String getPassword = password.getText().toString();
    int getWeight = Integer.parseInt(weight.getText().toString());
    long newId = myDB.insertRow(getUsername, getPassword, getWeight);

    Cursor cursor = myDB.getRow(newId);
    displayRecordSet(cursor);
}

public void onClick_ClearAll(View v) {

    myDB.deleteAll();
}

public void onClick_DisplayRecords(View v) {


    Cursor cursor = myDB.getAllRows();
    displayRecordSet(cursor);
}


    private void displayRecordSet(Cursor cursor) {
        String message = "";

        if (cursor.moveToFirst()) {
            do {

                int id = cursor.getInt(DBAdapter.COL_ROWID);
                String name = cursor.getString(DBAdapter.COL_NAME);
                String password = cursor.getString(DBAdapter.COL_PASSWORD);
                int weight = Integer.parseInt(cursor.getString(DBAdapter.COL_WEIGHT));


                message += "id=" + id
                           +", name=" + name
                           +", #=" + password
                           +", Colour=" + weight
                           +"\n";
            } while(cursor.moveToNext());
        }
        cursor.close();

        displayText(message);
    }



@Override
public boolean onCreateOptionsMenu(Menu menu) {
    getMenuInflater().inflate(R.menu.current_users, menu);
    return true;
}

}

Xml：

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical" >

<FrameLayout
    android:layout_width="match_parent"
    android:layout_height="0dp"
    android:layout_weight="0.16" >

    <TextView
        android:id="@+id/textView1"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:paddingLeft="220dp"
        android:text="@string/title_activity_current_users"
        android:textSize="25sp"
        android:textStyle="bold" />

    <TextView
        android:id="@+id/textView2"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:paddingTop="100dp"
        android:text="@string/name" />

    <TextView
        android:id="@+id/textView3"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:paddingLeft="200dp"
        android:paddingTop="100dp"
        android:text="@string/timein" />

    <TextView
        android:id="@+id/textView4"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:paddingLeft="400dp"
        android:paddingTop="100dp"
        android:text="@string/score" />

    <TextView
        android:id="@+id/textView5"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:paddingLeft="540dp"
        android:paddingTop="100dp"
        android:text="@string/done" />

    <Button
        android:id="@+id/regbut"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="@string/register" />

    <Button
        android:id="@+id/addbut"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginLeft="505dp"
        android:onClick="onClick_ClearAll"
        android:text="@string/adduser" />

</FrameLayout>

<ScrollView
    android:layout_width="match_parent"
    android:layout_height="0dp"
    android:layout_weight="1" >


    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:orientation="vertical" >

        <TextView
            android:id="@+id/textdisp"
            android:layout_width="match_parent"
            android:layout_height="2000dp"
             />

    </LinearLayout>

</ScrollView>

</LinearLayout>

PopupWindow Xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical"
android:background="@android:color/darker_gray" >

<TextView
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:text="@string/register"
    android:textSize="20sp" />

    <TextView
    android:text="@string/desireduser"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    /> 
    <EditText
     android:id="@+id/usertext"
      android:layout_width="match_parent"
      android:layout_height="wrap_content"  
      android:inputType="text"
        />

        <TextView
    android:text="@string/desiredpass"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    />

        <EditText
            android:id="@+id/passwordtext"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:ems="10"

            android:inputType="textPassword"
             />
     <TextView
    android:text="@string/weightinpounds"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    />

     <EditText
            android:id="@+id/weight"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:ems="10"
            android:inputType="number"
             />

    <Button
        android:id="@+id/register"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:onClick="registerUser"
        android:text="@string/register2" />

    <Button
        android:id="@+id/close"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="@string/close" />

</LinearLayout>

我已经尝试过不使用editTexts，但是它仍然相同。请帮我谢谢！

编辑这是logcat（对不起）

08-18 14:42:43.062: E/AndroidRuntime(9748): FATAL EXCEPTION: main
08-18 14:42:43.062: E/AndroidRuntime(9748): java.lang.IllegalStateException: Could not                 execute method of the activity
08-18 14:42:43.062: E/AndroidRuntime(9748):     at     android.view.View$1.onClick(View.java:3599)
08-18 14:42:43.062: E/AndroidRuntime(9748):     at android.view.View.performClick(View.java:4204)
08-18 14:42:43.062: E/AndroidRuntime(9748):     at android.view.View$PerformClick.run(View.java:17355)
08-18 14:42:43.062: E/AndroidRuntime(9748):     at android.os.Handler.handleCallback(Handler.java:725)
08-18 14:42:43.062: E/AndroidRuntime(9748):     at android.os.Handler.dispatchMessage(Handler.java:92)
08-18 14:42:43.062: E/AndroidRuntime(9748):     at android.os.Looper.loop(Looper.java:137)
08-18 14:42:43.062: E/AndroidRuntime(9748):     at android.app.ActivityThread.main(ActivityThread.java:5041)
08-18 14:42:43.062: E/AndroidRuntime(9748):     at java.lang.reflect.Method.invokeNative(Native Method)
08-18 14:42:43.062: E/AndroidRuntime(9748):     at java.lang.reflect.Method.invoke(Method.java:511)
08-18 14:42:43.062: E/AndroidRuntime(9748):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793)
08-18 14:42:43.062: E/AndroidRuntime(9748):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560)
08-18 14:42:43.062: E/AndroidRuntime(9748):     at dalvik.system.NativeStart.main(Native Method)
08-18 14:42:43.062: E/AndroidRuntime(9748): Caused by: java.lang.reflect.InvocationTargetException
08-18 14:42:43.062: E/AndroidRuntime(9748):     at java.lang.reflect.Method.invokeNative(Native Method)
08-18 14:42:43.062: E/AndroidRuntime(9748):     at java.lang.reflect.Method.invoke(Method.java:511)
08-18 14:42:43.062: E/AndroidRuntime(9748):     at android.view.View$1.onClick(View.java:3594)
08-18 14:42:43.062: E/AndroidRuntime(9748):     ... 11 more
08-18 14:42:43.062: E/AndroidRuntime(9748): Caused by: java.lang.NullPointerException
08-18 14:42:43.062: E/AndroidRuntime(9748):     at com.example.istronggyminstructor.CurrentUsers.registerUser(CurrentUsers.java:75)
08-18 14:42:43.062: E/AndroidRuntime(9748):     ... 14 more

阿尼鲁达（Aniruddha）

可能myDB为null（因为您没有提供完整的堆栈跟踪）。

在执行任何数据库操作之前，请打开数据库。因此，您需要openDB()在执行任何与数据库相关的操作之前调用该方法。

无需初始化，myDB您正在执行DB操作，即myDB.insertRow(getUsername, getPassword, getWeight);AND Cursor cursor = myDB.getRow(newId);。这myDB是null，因为您尚未初始化它，即myDB = new DBAdapter(this)

编辑

您有2个选择。1）将View popupview变量设为全局。然后更换

View popupview=inflator.inflate(R.layout.popup, null);

经过

popupview=inflator.inflate(R.layout.popup, null);

然后在方法里面registerUser(View v)，更换

EditText username = (EditText)findViewById(R.id.usertext);
EditText password = (EditText)findViewById(R.id.passwordtext);
EditText weight = (EditText)findViewById(R.id.weight);

经过

EditText username = (EditText)popupview.findViewById(R.id.usertext);
EditText password = (EditText)popupview.findViewById(R.id.passwordtext);
EditText weight = (EditText)popupview.findViewById(R.id.weight);

2）移动

EditText username = (EditText)findViewById(R.id.usertext);
EditText password = (EditText)findViewById(R.id.passwordtext);
EditText weight = (EditText)findViewById(R.id.weight);

从registerUser(View v)然后粘贴

Button dismissbtn = (Button)popupview.findViewById(R.id.close);

所以应该看起来像这样

Button dismissbtn = (Button)popupview.findViewById(R.id.close);
EditText username = (EditText)popupview.findViewById(R.id.usertext);
EditText password = (EditText)popupview.findViewById(R.id.passwordtext);
EditText weight = (EditText)popupview.findViewById(R.id.weight);

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