问题
您好，我在引用我正在制作的 Android 应用程序上的按钮时遇到问题。问题是引用按钮的空指针，我很困惑为什么会发生这种情况。另一个类上有一个非常相似的引用，我已将其包含在内以供引用(welcomeScreen.java 的 onTestButtonClickr)
编辑
我发现如果我更改 setContentView(R.layout.activity_in_game);设置ContentView(R.layout.fragment_in_game);空指针消失，但我对按钮所做的任何更改都不起作用
日志猫
04-14 13:13:40.280: D/dalvikvm(838): Not late-enabling CheckJNI (already on)
04-14 13:13:43.330: D/dalvikvm(838): GC_FOR_ALLOC freed 72K, 5% free 2993K/3132K, paused 167ms, total 169ms
04-14 13:13:44.280: D/dalvikvm(838): GC_FOR_ALLOC freed 3K, 5% free 3382K/3524K, paused 154ms, total 154ms
04-14 13:13:45.310: D/dalvikvm(838): GC_FOR_ALLOC freed 8K, 3% free 3802K/3916K, paused 194ms, total 194ms
04-14 13:13:45.590: D/gralloc_goldfish(838): Emulator without GPU emulation detected.
04-14 13:13:59.570: I/Choreographer(838): Skipped 33 frames! The application may be doing too much work on its main thread.
04-14 13:14:01.030: D/AndroidRuntime(838): Shutting down VM
04-14 13:14:01.030: W/dalvikvm(838): threadid=1: thread exiting with uncaught exception (group=0xb2aabba8)
04-14 13:14:01.080: E/AndroidRuntime(838): FATAL EXCEPTION: main
04-14 13:14:01.080: E/AndroidRuntime(838): Process: com.moconnell.thehacker, PID: 838
04-14 13:14:01.080: E/AndroidRuntime(838): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.moconnell.thehacker/com.moconnell.thehacker.InGame}: java.lang.NullPointerException
04-14 13:14:01.080: E/AndroidRuntime(838): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2195)
04-14 13:14:01.080: E/AndroidRuntime(838): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2245)
04-14 13:14:01.080: E/AndroidRuntime(838): at android.app.ActivityThread.access$800(ActivityThread.java:135)
04-14 13:14:01.080: E/AndroidRuntime(838): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1196)
04-14 13:14:01.080: E/AndroidRuntime(838): at android.os.Handler.dispatchMessage(Handler.java:102)
04-14 13:14:01.080: E/AndroidRuntime(838): at android.os.Looper.loop(Looper.java:136)
04-14 13:14:01.080: E/AndroidRuntime(838): at android.app.ActivityThread.main(ActivityThread.java:5017)
04-14 13:14:01.080: E/AndroidRuntime(838): at java.lang.reflect.Method.invokeNative(Native Method)
04-14 13:14:01.080: E/AndroidRuntime(838): at java.lang.reflect.Method.invoke(Method.java:515)
04-14 13:14:01.080: E/AndroidRuntime(838): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:779)
04-14 13:14:01.080: E/AndroidRuntime(838): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:595)
04-14 13:14:01.080: E/AndroidRuntime(838): at dalvik.system.NativeStart.main(Native Method)
04-14 13:14:01.080: E/AndroidRuntime(838): Caused by: java.lang.NullPointerException
04-14 13:14:01.080: E/AndroidRuntime(838): at com.moconnell.thehacker.InGame.generateImages(InGame.java:195)
04-14 13:14:01.080: E/AndroidRuntime(838): at com.moconnell.thehacker.InGame.onCreate(InGame.java:64)
04-14 13:14:01.080: E/AndroidRuntime(838): at android.app.Activity.performCreate(Activity.java:5231)
04-14 13:14:01.080: E/AndroidRuntime(838): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1087)
04-14 13:14:01.080: E/AndroidRuntime(838): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2159)
04-14 13:14:01.080: E/AndroidRuntime(838): ... 11 more
04-14 13:14:03.760: I/Process(838): Sending signal. PID: 838 SIG: 9
有错误的类
package com.moconnell.thehacker;
import java.io.File;
import java.lang.reflect.Field;
import java.util.ArrayList;
import java.util.ResourceBundle;
import android.support.v7.app.ActionBarActivity;
import android.support.v7.app.ActionBar;
import android.support.v4.app.Fragment;
import android.content.Intent;
import android.content.res.Resources;
import android.graphics.Color;
import android.graphics.drawable.Drawable;
import android.os.Bundle;
import android.os.Environment;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.view.ViewGroup;
import android.widget.Button;
import android.widget.ImageButton;
import android.widget.ImageView;
import android.widget.TextView;
import android.os.Build;
public class InGame extends ActionBarActivity {
//public ImageButton mBtn;
ImageButton currentImage;
//public ArrayList<Drawable> j;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_in_game);
//mBtn = (ImageButton) findViewById(R.id.ImageButton1_2);
//mBtn.setImageResource(R.drawable.fat_banana);
//
//
// btn.setOnClickListener(new View.OnClickListener() {
// @Override
// public void onClick(View v) {
// btn.setBackgroundColor(Color.GREEN);
// //evaluateSubmission(v);
// }
// });
//
// Resources resources = com.moconnell.thehacker.WelcomeScreen.getResources();
// j= new ArrayList<Drawable>();
// j.add(resources.getDrawable(R.drawable.a_button));
// j.add(resources.getDrawable(R.drawable.b_button));
// j.add(resources.getDrawable(R.drawable.c_button));
// j.add(resources.getDrawable(R.drawable.d_button));
// j.add(resources.getDrawable(R.drawable.e_button));
//
generateImages();
if (savedInstanceState == null) {
getSupportFragmentManager().beginTransaction()
.add(R.id.container, new PlaceholderFragment()).commit();
}
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.in_game, 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();
if (id == R.id.action_settings) {
return true;
}
return super.onOptionsItemSelected(item);
}
/**
* A placeholder fragment containing a simple view.
*/
public static class PlaceholderFragment extends Fragment {
public PlaceholderFragment() {
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.fragment_in_game,
container, false);
return rootView;
}
}
//final TextView txtDir = (TextView) findViewById(R.id.txtDirections);
public void onTestButtonClickr(View view)
{
startActivity(new Intent("com.moconnell.thehacker.WelcomeScreen"));
}
public void click(View v)
{
//txtDir.setText("eed");//startActivity(new Intent("com.moconnell.thehacker.InGame"));
}
public void evaluateButton(View view)
{
ImageButton b = (ImageButton)view;
currentImage = (ImageButton)findViewById(R.id.ImageButton1_6);
Log.v("", "currentImage:" + currentImage.getResources());
//Log.v("", "buttnID:" + b.getId());
if( b.getId()==R.id.ImageButton1_5)
Log.v("", "1,5");
if( b.getId()==R.id.ImageButton2_5)
Log.v("", "2,5");
if( b.getId()==R.id.ImageButton3_5)
Log.v("", "3,5");
//Log.v("","buttonpressed:"+ b.getdi);
}
public void generateImages()
{
ImageButton b16 = (ImageButton)findViewById(R.id.ImageButton1_6);
Log.v("", "b16:" + b16.toString());
Log.v("", "pic:" + com.moconnell.thehacker.WelcomeScreen.j.get(1));
// b12.setImageDrawable(com.moconnell.thehacker.WelcomeScreen.j.get(1));
\
//int id = getResources().getIdentifier("thehacker/drawable/" + "a_button.png", null, null);
// b12.setImageDrawable(resources.getDrawable(R.drawable.e_button));
//b13.setImageResource(id);
// b14.setImageDrawable(j.get(2));
// Log.v("", b13.toString());
// Log.v("", j.get(1));
}
}
其他可供引用的类
package com.moconnell.thehacker;
import java.util.ArrayList;
import android.support.v7.app.ActionBarActivity;
import android.support.v7.app.ActionBar;
import android.support.v4.app.Fragment;
import android.content.Intent;
import android.content.res.Resources;
import android.graphics.Color;
import android.graphics.drawable.Drawable;
import android.os.Bundle;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.view.View.OnClickListener;
import android.view.ViewGroup;
import android.widget.Button;
import android.widget.ImageView;
import android.os.Build;
public class WelcomeScreen extends ActionBarActivity {
public Button btnNewGame;
public Button mBtn;
public static ArrayList<Drawable> j;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
btnNewGame = (Button) findViewById(R.id.btnNewGame);
//btnNewGame.setOnClickListener(this);
////////////////////////////////////////////////////////////////
/////////////////////////////////////////////////////////
// Button toggleButton = (Button) findViewById(R.id.btnHighScore);
// final ImageView img = (ImageView) findViewById(R.id.ImageView01);
// toggleButton.setOnClickListener(
//
// new View.OnClickListener() {
//
// public void onClick(View v) {
// img.setImageResource(R.drawable.fat_banana);
// }
//
// });
//////////////////////////////////////////////////////////////////////
///////////////////////////////////////////////////////////////////////
Resources resources = getResources();
j= new ArrayList<Drawable>();
j.add(resources.getDrawable(R.drawable.a_button));
j.add(resources.getDrawable(R.drawable.b_button));
j.add(resources.getDrawable(R.drawable.c_button));
j.add(resources.getDrawable(R.drawable.d_button));
j.add(resources.getDrawable(R.drawable.e_button));
if (savedInstanceState == null) {
getSupportFragmentManager().beginTransaction()
.add(R.id.container, new PlaceholderFragment()).commit();
}
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.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();
if (id == R.id.action_settings) {
return true;
}
return super.onOptionsItemSelected(item);
}
/**
* A placeholder fragment containing a simple view.
*/
public static class PlaceholderFragment extends Fragment {
public PlaceholderFragment() {
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.fragment_main, container,
false);
return rootView;
}
}
public void onTestButtonClick(View view)
{
startActivity(new Intent("com.moconnell.thehacker.InGame"));
}
public void highScores(View view)
{
}
public void onTestButtonClickr(View view)
{
Button b = (Button)view;
String buttonText = b.getText().toString();
Log.v("", "butText:" + buttonText);
b.setText("cc");
Log.v("", "buttnID:" + b.getId());
if( b.getId()==R.id.btnNewGame)
Log.v("", "thsi is the new game button");
if( b.getId()==R.id.btnHighScore)
Log.v("", "thsi is the high scores button");
ImageView i = (ImageView)findViewById(R.id.ImageView01);
// .setImageResource(R.drawable.fat_banana);
Log.v("", "dispImg:" + i.getId());
Resources resources = getResources();
//i.setImageDrawable(resources.getDrawable(R.drawable.fat_banana));
i.setImageDrawable(j.get(1));
// if(buttonText.equals("View High Scores"))
// startActivity(new Intent("com.moconnell.thehacker.InGame"));
}
// private void empezarNewGame()
// {
//
// }
//
}
fragment_ingame
<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:id="@+id/container"
android:background="@drawable/background_tron"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context="com.moconnell.thehacker.WelcomeScreen"
tools:ignore="MergeRootFrame"
android:orientation="vertical">
<TableLayout
android:layout_width="match_parent"
android:layout_height="match_parent"
android:paddingLeft="5dp"
android:paddingRight="5dp"
android:paddingTop="10dp"
android:gravity="center">
<Button
android:id="@+id/buttonReturn"
style="?android:attr/buttonStyleSmall"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Button"
android:onClick="onTestButtonClickr"
/>
<ImageView
android:id="@+id/imageView1"
android:layout_width="wrap_content"
android:layout_height="53dp"
android:onClick="click"
android:src="@drawable/a_button"
android:gravity="center"/>
<TableRow
android:id="@+id/tableRow01"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:gravity="center">
<ImageButton
android:id="@+id/ImageButton1_6"
android:layout_width="50dp"
android:layout_height="50dp"
android:src="@drawable/a_display" />
<ImageButton
android:id="@+id/ImageButton2_6"
android:layout_width="50dp"
android:layout_height="50dp"
android:src="@drawable/b_display" />
<ImageButton
android:id="@+id/ImageButton3_6"
android:layout_width="50dp"
android:layout_height="50dp"
android:src="@drawable/c_display" />
<ImageButton
android:id="@+id/ImageButton4_6"
android:layout_width="50dp"
android:layout_height="50dp"
android:src="@drawable/d_display" />
<ImageButton
android:id="@+id/ImageButton5_6"
android:layout_width="50dp"
android:layout_height="50dp"
android:src="@drawable/e_display" />
</TableRow>
<TextView
android:id="@+id/txtDirections"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Enter the above code open lock"
android:textAppearance="?android:attr/textAppearanceMedium"
android:gravity="center" />
<TableRow
android:id="@+id/TableRow02"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:gravity="center">
<ImageButton
android:id="@+id/ImageButton1_5"
android:layout_width="50dp"
android:layout_height="50dp"
android:src="@drawable/loading"
android:onClick="evaluateButton"/>
<ImageButton
android:id="@+id/ImageButton2_5"
android:layout_width="50dp"
android:layout_height="50dp"
android:src="@drawable/loading"
android:onClick="evaluateButton"/>
<ImageButton
android:id="@+id/ImageButton3_5"
android:layout_width="50dp"
android:layout_height="50dp"
android:src="@drawable/loading"
android:onClick="evaluateButton" />
<ImageButton
android:id="@+id/ImageButton4_5"
android:layout_width="50dp"
android:layout_height="50dp"
android:src="@drawable/loading"
android:onClick="evaluateButton"/>
<ImageButton
android:id="@+id/ImageButton5_5"
android:layout_width="50dp"
android:layout_height="50dp"
android:src="@drawable/loading"
android:onClick="evaluateButton"/>
</TableRow>
<TableRow
android:id="@+id/TableRow03"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:gravity="center" >
<ImageButton
android:id="@+id/ImageButton1_4"
android:layout_width="50dp"
android:layout_height="50dp"
android:src="@drawable/loading"
android:onClick="evaluateButton" />
<ImageButton
android:id="@+id/ImageButton2_4"
android:layout_width="50dp"
android:layout_height="50dp"
android:src="@drawable/loading"
android:onClick="evaluateButton" />
<ImageButton
android:id="@+id/ImageButton3_4"
android:layout_width="50dp"
android:layout_height="50dp"
android:src="@drawable/loading"
android:onClick="evaluateButton" />
<ImageButton
android:id="@+id/ImageButton4_4"
android:layout_width="50dp"
android:layout_height="50dp"
android:src="@drawable/loading"
android:onClick="evaluateButton" />
<ImageButton
android:id="@+id/ImageButton5_4"
android:layout_width="50dp"
android:layout_height="50dp"
android:src="@drawable/loading"
android:onClick="evaluateButton" />
</TableRow>
<TableRow
android:id="@+id/tableRow6"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:gravity="center" >
<ImageButton
android:id="@+id/ImageButton1_3"
android:layout_width="50dp"
android:layout_height="50dp"
android:src="@drawable/loading"
android:onClick="evaluateButton"/>
<ImageButton
android:id="@+id/ImageButton2_3"
android:layout_width="50dp"
android:layout_height="50dp"
android:src="@drawable/loading"
android:onClick="evaluateButton"/>
<ImageButton
android:id="@+id/ImageButton3_3"
android:layout_width="50dp"
android:layout_height="50dp"
android:src="@drawable/loading"
android:onClick="evaluateButton" />
<ImageButton
android:id="@+id/ImageButton4_3"
android:layout_width="50dp"
android:layout_height="50dp"
android:src="@drawable/loading"
android:onClick="evaluateButton" />
<ImageButton
android:id="@+id/ImageButton5_3"
android:layout_width="50dp"
android:layout_height="50dp"
android:src="@drawable/loading"
android:onClick="evaluateButton"/>
</TableRow>
<TableRow
android:id="@+id/tableRow5"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:gravity="center">
<ImageButton
android:id="@+id/ImageButton1_2"
android:layout_width="50dp"
android:layout_height="50dp"
android:src="@drawable/loading"
android:onClick="evaluateButton"/>
<ImageButton
android:id="@+id/ImageButton2_2"
android:layout_width="50dp"
android:layout_height="50dp"
android:src="@drawable/loading"
android:onClick="evaluateButton" />
<ImageButton
android:id="@+id/ImageButton3_2"
android:layout_width="50dp"
android:layout_height="50dp"
android:src="@drawable/loading"
android:onClick="evaluateButton"/>
<ImageButton
android:id="@+id/ImageButton4_2"
android:layout_width="50dp"
android:layout_height="50dp"
android:src="@drawable/loading"
android:onClick="evaluateButton"/>
<ImageButton
android:id="@+id/ImageButton5_2"
android:layout_width="50dp"
android:layout_height="50dp"
android:src="@drawable/loading"
android:onClick="evaluateButton" />
</TableRow>
</TableLayout>
</FrameLayout>
游戏中的 Activity
<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:id="@+id/container"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context="com.moconnell.thehacker.InGame"
tools:ignore="MergeRootFrame" />
最佳答案
您在附加具有 View 资源fragment_ingame的 fragment 之前调用generateImages()函数。因此，在generateImages()中，没有ID为R.id.ImageButton1_6的ImageButton可用。
关于java - 空指针搜索 findViewById android 应用程序 Java，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/23066525/