我是 Android 的新手，这是我的主要活动。我在每个项目中都遇到了这个错误：
import android.os.Bundle;
import android.app.Activity;
import android.view.Menu;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.EditText;
public class MainActivity extends Activity {
Button btnone,btntwo,btnthree,btnfour,btnfive,btnsix,btnseven,btneight,btnnine,btnzeo,btnstar,btnhash,btndial,btnbackspace;
EditText etnum;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
btnone = (Button)findViewById(R.id.btnone);
btntwo = (Button)findViewById(R.id.btntwo);
btnthree = (Button)findViewById(R.id.btnthree);
btnfour = (Button)findViewById(R.id.btfour);
btnfive = (Button)findViewById(R.id.btnfive);
btnsix = (Button)findViewById(R.id.btnsix);
btnseven = (Button)findViewById(R.id.btnseven);
btneight = (Button)findViewById(R.id.btneight);
btnnine = (Button)findViewById(R.id.btnnine);
btnzeo = (Button)findViewById(R.id.btnzero);
btnstar = (Button)findViewById(R.id.btnstar);
btnhash = (Button)findViewById(R.id.btnhash);
btndial = (Button)findViewById(R.id.btncall);
btnbackspace = (Button)findViewById(R.id.btnbacspace);
etnum = (EditText) findViewById(R.id.etnumbr);
btnone.setOnClickListener((OnClickListener)this);
btntwo.setOnClickListener((OnClickListener)this);
btnthree.setOnClickListener((OnClickListener)this);
btnfour.setOnClickListener((OnClickListener)this);
btnfive.setOnClickListener((OnClickListener)this);
btnsix.setOnClickListener((OnClickListener)this);
btnseven.setOnClickListener((OnClickListener)this);
btneight.setOnClickListener((OnClickListener)this);
btnnine.setOnClickListener((OnClickListener)this);
btnzeo.setOnClickListener((OnClickListener)this);
btnstar.setOnClickListener((OnClickListener)this);
btnhash.setOnClickListener((OnClickListener)this);
btndial.setOnClickListener((OnClickListener)this);
btnbackspace.setOnClickListener((OnClickListener)this);
etnum.setOnClickListener((OnClickListener)this);
}
@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;
}
}
这是我的 logcat 日志，我几乎在每个项目中都会遇到这个错误：
05-01 23:18:40.364: E/AndroidRuntime(5668): FATAL EXCEPTION: main
05-01 23:18:40.364: E/AndroidRuntime(5668): java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{com.casbwp.mydialerapp/com.casbwp.mydialerapp.MainActivity}: java.lang.ClassNotFoundException: Didn't find class "com.casbwp.mydialerapp.MainActivity" on path: /data/app/com.casbwp.mydialerapp-1.apk
05-01 23:18:40.364: E/AndroidRuntime(5668): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2106)
05-01 23:18:40.364: E/AndroidRuntime(5668): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2230)
05-01 23:18:40.364: E/AndroidRuntime(5668): at android.app.ActivityThread.access$600(ActivityThread.java:141)
05-01 23:18:40.364: E/AndroidRuntime(5668): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1234)
05-01 23:18:40.364: E/AndroidRuntime(5668): at android.os.Handler.dispatchMessage(Handler.java:99)
05-01 23:18:40.364: E/AndroidRuntime(5668): at android.os.Looper.loop(Looper.java:137)
05-01 23:18:40.364: E/AndroidRuntime(5668): at android.app.ActivityThread.main(ActivityThread.java:5039)
05-01 23:18:40.364: E/AndroidRuntime(5668): at java.lang.reflect.Method.invokeNative(Native Method)
05-01 23:18:40.364: E/AndroidRuntime(5668): at java.lang.reflect.Method.invoke(Method.java:511)
05-01 23:18:40.364: E/AndroidRuntime(5668): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793)
05-01 23:18:40.364: E/AndroidRuntime(5668): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560)
05-01 23:18:40.364: E/AndroidRuntime(5668): at dalvik.system.NativeStart.main(Native Method)
05-01 23:18:40.364: E/AndroidRuntime(5668): Caused by: java.lang.ClassNotFoundException: Didn't find class "com.casbwp.mydialerapp.MainActivity" on path: /data/app/com.casbwp.mydialerapp-1.apk
05-01 23:18:40.364: E/AndroidRuntime(5668): at dalvik.system.BaseDexClassLoader.findClass(BaseDexClassLoader.java:65)
05-01 23:18:40.364: E/AndroidRuntime(5668): at java.lang.ClassLoader.loadClass(ClassLoader.java:501)
05-01 23:18:40.364: E/AndroidRuntime(5668): at java.lang.ClassLoader.loadClass(ClassLoader.java:461)
05-01 23:18:40.364: E/AndroidRuntime(5668): at android.app.Instrumentation.newActivity(Instrumentation.java:1054)
05-01 23:18:40.364: E/AndroidRuntime(5668): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2097)
05-01 23:18:40.364: E/AndroidRuntime(5668): ... 11 more
这是我的 xml 文件：
<TableLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:id="@+id/TableLayout1"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:minHeight="30dp"
android:minWidth="50dp"
android:nextFocusDown="@string/btn0"
android:paddingBottom="@dimen/activity_vertical_margin"
android:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
tools:context=".MainActivity" >
<TableRow
android:id="@+id/tblrow"
android:layout_width="wrap_content"
android:layout_height="wrap_content" >
<LinearLayout
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:orientation="horizontal" >
<EditText
android:id="@+id/etnumbr"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:ems="10"
android:inputType="number" >
<requestFocus />
</EditText>
</LinearLayout>
</TableRow>
<android.support.v7.widget.Space
android:id="@+id/space1"
android:layout_width="wrap_content"
android:layout_height="wrap_content" />
<TableRow
android:id="@+id/tblrow2"
android:layout_width="wrap_content"
android:layout_height="wrap_content" >
</TableRow>
<TableRow
android:id="@+id/tableRow4"
android:layout_width="wrap_content"
android:layout_height="wrap_content" >
<LinearLayout
android:layout_width="wrap_content"
android:layout_height="wrap_content" >
<Button
android:id="@+id/btnone"
android:layout_width="95dp"
android:layout_height="80dp"
android:text="@string/btn1" />
<Button
android:id="@+id/btntwo"
android:layout_width="95dp"
android:layout_height="80dp"
android:text="@string/btn2" />
<Button
android:id="@+id/btnthree"
android:layout_width="95dp"
android:layout_height="80dp"
android:text="@string/btn3" />
</LinearLayout>
</TableRow>
<TableRow
android:id="@+id/tableRow6"
android:layout_width="wrap_content"
android:layout_height="wrap_content" >
<LinearLayout
android:layout_width="wrap_content"
android:layout_height="wrap_content" >
<Button
android:id="@+id/btfour"
android:layout_width="95dp"
android:layout_height="80dp"
android:text="@string/btn4" />
<Button
android:id="@+id/btnfive"
android:layout_width="95dp"
android:layout_height="80dp"
android:text="@string/btn5" />
<Button
android:id="@+id/btnsix"
android:layout_width="95dp"
android:layout_height="80dp"
android:text="@string/btn6" />
</LinearLayout>
</TableRow>
<TableRow
android:id="@+id/tableRow5"
android:layout_width="wrap_content"
android:layout_height="wrap_content" >
<LinearLayout
android:layout_width="wrap_content"
android:layout_height="wrap_content" >
<Button
android:id="@+id/btnseven"
android:layout_width="95dp"
android:layout_height="80dp"
android:text="@string/btn7" />
<Button
android:id="@+id/btneight"
android:layout_width="95dp"
android:layout_height="80dp"
android:text="@string/btn8" />
<Button
android:id="@+id/btnnine"
android:layout_width="95dp"
android:layout_height="80dp"
android:text="@string/btn9" />
</LinearLayout>
</TableRow>
<TableRow
android:id="@+id/tableRow1"
android:layout_width="wrap_content"
android:layout_height="wrap_content" >
<LinearLayout
android:layout_width="wrap_content"
android:layout_height="wrap_content" >
<Button
android:id="@+id/btnstar"
android:layout_width="95dp"
android:layout_height="80dp"
android:text="@string/btnstar" />
<Button
android:id="@+id/btnzero"
android:layout_width="95dp"
android:layout_height="80dp"
android:text="@string/btn0" />
<Button
android:id="@+id/btnhash"
android:layout_width="95dp"
android:layout_height="80dp"
android:text="@string/btnhash" />
</LinearLayout>
</TableRow>
<TableRow
android:id="@+id/tableRow2"
android:layout_width="wrap_content"
android:layout_height="wrap_content" >
<LinearLayout
android:layout_width="wrap_content"
android:layout_height="wrap_content" >
<Button
android:id="@+id/btncall"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_weight="0.44"
android:background="@drawable/ic_action_call"
android:text="@string/btnDial" />
<Button
android:id="@+id/btnbacspace"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_weight="0.45"
android:background="@drawable/ic_action_delete"
android:text="@string/btnbackspace" />
</LinearLayout>
</TableRow>
</TableLayout>