I am new to ANDROID development.I followed the topics in “Hello,Android(3rd Edition)”. Until chapter 3.4 “Using Alternate Resources” it works fine… But in 3.5 “Implementing an About Box” i did all the steps given in the book. But when i try to run in simulator, it displays Unfortunately, Sudoku has stopped.. I don’t know what was wrong!
My activity_main.xml file
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
tools:context=".MainActivity"
android:background="@color/background"
android:padding="30dip"
android:layout_gravity="center"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:orientation="vertical">
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="@string/main_title"
android:layout_gravity="center"
android:textSize="25sp"
android:layout_marginBottom="25dip" />
<Button
android:id="@+id/continue_button"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:text="@string/continue_label" />
<Button
android:id="@+id/new_game_button"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="@string/new_game_label" />
<Button
android:id="@+id/about_button"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:text="@string/about_label" />
<Button
android:id="@+id/exit_button"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:text="@string/exit_label" />
</LinearLayout>
my about.xml file
<?xml version="1.0" encoding="utf-8"?>
<ScrollView xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:padding="30dip" >
<TextView
android:id="@+id/about_content"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="@string/about_text" />
</ScrollView>
my strings.xml file
<?xml version="1.0" encoding="utf-8"?>
<resources>
<string name="app_name">Sudoku</string>
<string name="main_title">SUDOKU</string>
<string name="menu_settings">Settings</string>
<string name="continue_label">Continue</string>
<string name="new_game_label">New Game</string>
<string name="about_label">About</string>
<string name="exit_label">Exit</string>
<string name="about_title">About Sudoku</string>
<string name="about_text">\Sudoku is a logic-based number placement puzzle.
Starting with a partially completed 9x9 grid, the
objective is to fill the grid so that each
row, each column, and each of the 3x3 boxes
(also called blocks) contains the digits
1 to 9 exactly once.</string>
</resources>
my MainActivity.java file
package org.example.sudoku;
import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.view.Menu;
import android.view.View;
import android.view.View.OnClickListener;
public class MainActivity extends Activity implements OnClickListener {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
// Set up click listeners for all the buttons
View continueButton = findViewById(R.id.continue_button);
continueButton.setOnClickListener(this);
View newButton = findViewById(R.id.new_button);
newButton.setOnClickListener(this);
View aboutButton = findViewById(R.id.about_button);
aboutButton.setOnClickListener(this);
View exitButton = findViewById(R.id.exit_button);
exitButton.setOnClickListener(this);
}
@Override
public void onClick(View v) {
switch (v.getId()) {
case R.id.about_button:
Intent i = new Intent(this, About.class);
startActivity(i);
break;
// More buttons go here (if any) ...
}
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.activity_main, menu);
return true;
}
}
my About.java file
package org.example.sudoku;
import android.app.Activity;
import android.os.Bundle;
public class About extends Activity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.about);
}
}
my AndroidManifest.xml file
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="org.example.sudoku"
android:versionCode="1"
android:versionName="1.0" >
<uses-sdk
android:minSdkVersion="8"
android:targetSdkVersion="17" />
<application
android:allowBackup="true"
android:icon="@drawable/ic_launcher"
android:label="@string/app_name"
android:theme="@style/AppTheme" >
<activity
android:name="org.example.sudoku.MainActivity"
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="org.example.sudoku.About"
android:label="@string/about_title" >
</activity>
</application>
</manifest>
my log file
02-07 02:37:39.678: W/Trace(787): Unexpected value from nativeGetEnabledTags: 0
02-07 02:37:39.698: W/Trace(787): Unexpected value from nativeGetEnabledTags: 0
02-07 02:37:40.518: D/AndroidRuntime(787): Shutting down VM
02-07 02:37:40.538: W/dalvikvm(787): threadid=1: thread exiting with uncaught exception (group=0x40a70930)
02-07 02:37:40.568: E/AndroidRuntime(787): FATAL EXCEPTION: main
02-07 02:37:40.568: E/AndroidRuntime(787): java.lang.RuntimeException: Unable to start activity ComponentInfo{org.example.sudoku/org.example.sudoku.MainActivity}: java.lang.NullPointerException
02-07 02:37:40.568: E/AndroidRuntime(787): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2180)
02-07 02:37:40.568: E/AndroidRuntime(787): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2230)
02-07 02:37:40.568: E/AndroidRuntime(787): at android.app.ActivityThread.access$600(ActivityThread.java:141)
02-07 02:37:40.568: E/AndroidRuntime(787): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1234)
02-07 02:37:40.568: E/AndroidRuntime(787): at android.os.Handler.dispatchMessage(Handler.java:99)
02-07 02:37:40.568: E/AndroidRuntime(787): at android.os.Looper.loop(Looper.java:137)
02-07 02:37:40.568: E/AndroidRuntime(787): at android.app.ActivityThread.main(ActivityThread.java:5039)
02-07 02:37:40.568: E/AndroidRuntime(787): at java.lang.reflect.Method.invokeNative(Native Method)
02-07 02:37:40.568: E/AndroidRuntime(787): at java.lang.reflect.Method.invoke(Method.java:511)
02-07 02:37:40.568: E/AndroidRuntime(787): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793)
02-07 02:37:40.568: E/AndroidRuntime(787): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560)
02-07 02:37:40.568: E/AndroidRuntime(787): at dalvik.system.NativeStart.main(Native Method)
02-07 02:37:40.568: E/AndroidRuntime(787): Caused by: java.lang.NullPointerException
02-07 02:37:40.568: E/AndroidRuntime(787): at org.example.sudoku.MainActivity.onCreate(MainActivity.java:19)
02-07 02:37:40.568: E/AndroidRuntime(787): at android.app.Activity.performCreate(Activity.java:5104)
02-07 02:37:40.568: E/AndroidRuntime(787): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1080)
02-07 02:37:40.568: E/AndroidRuntime(787): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2144)
02-07 02:37:40.568: E/AndroidRuntime(787): ... 11 more
02-07 02:38:54.168: I/Process(787): Sending signal. PID: 787 SIG: 9
Help me to solve my problem….Thanks in advance….
This topic