您好我写了一个应用程序，登录后正确登录到另一页。这是主页面的代码，当我将它指向带有图像的普通页面时，它运行良好：
package com.example.loginscreen;
import android.app.Activity;
import android.content.Intent;
import android.graphics.Color;
import android.os.Bundle;
import android.view.Menu;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;
import android.widget.Toast;
public class MainActivity extends Activity {
private EditText username=null;
private EditText password=null;
private TextView attempts;
private Button login;
int counter = 3;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
username = (EditText)findViewById(R.id.editText1);
password = (EditText)findViewById(R.id.editText2);
attempts = (TextView)findViewById(R.id.textView5);
attempts.setText(Integer.toString(counter));
login = (Button)findViewById(R.id.button1);
}
public void login(View view){
if(username.getText().toString().equals("mark") &&
password.getText().toString().equals("mark")){
Toast.makeText(getApplicationContext(), "Login Successful!",
Toast.LENGTH_LONG).show();
startActivity(new Intent(MainActivity.this,Loading.class));
}
else{
Toast.makeText(getApplicationContext(), "Wrong Credentials",
Toast.LENGTH_SHORT).show();
attempts.setBackgroundColor(Color.RED);
counter--;
attempts.setText(Integer.toString(counter));
if(counter==0){
login.setEnabled(false);
}
}
}
@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;
}
}
通过以下活动切换到标签布局：
import android.app.Activity;
import android.os.Bundle;
import android.widget.TextView;
public class HomePage extends Activity {
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
TextView textview = new TextView(this);
textview.setText("Overview");
setContentView(textview);
}
}
package com.example.loginscreen;
import android.app.Activity;
import android.os.Bundle;
import android.widget.TextView;
public class HomePage2 extends Activity {
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
TextView textview = new TextView(this);
textview.setText("Card Summary");
setContentView(textview);
}
}
package com.example.loginscreen;
import android.app.Activity;
import android.os.Bundle;
import android.widget.TextView;
public class HomePage3 extends Activity {
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
TextView textview = new TextView(this);
textview.setText("Details");
setContentView(textview);
}
}
所有这些都通过这个链接：
package com.example.loginscreen;
import android.app.TabActivity;
import android.content.Intent;
import android.content.res.Resources;
import android.os.Bundle;
import android.widget.TabHost;
import android.widget.TabHost.TabSpec;
@SuppressWarnings("deprecation")
public class LinkTabs extends TabActivity {
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.link_main);
Resources ressources = getResources();
TabHost tabHost = getTabHost();
// First tab
Intent intentAndroid = new Intent().setClass(this, HomePage.class);
TabSpec tabSpecHomePage = tabHost
.newTabSpec("HomePage")
.setIndicator("", ressources.getDrawable(R.drawable.overview))
.setContent(intentAndroid);
// Second tab
Intent intentApple = new Intent().setClass(this, HomePage2.class);
TabSpec tabSpecHomePage2 = tabHost
.newTabSpec("HomePage2")
.setIndicator("", ressources.getDrawable(R.drawable.overview))
.setContent(intentApple);
// Third tab
Intent intentWindows = new Intent().setClass(this, HomePage3.class);
TabSpec tabSpecHomePage3 = tabHost
.newTabSpec("HomePage3")
.setIndicator("", ressources.getDrawable(R.drawable.overview))
.setContent(intentWindows);
// add all tabs
tabHost.addTab(tabSpecHomePage);
tabHost.addTab(tabSpecHomePage2);
tabHost.addTab(tabSpecHomePage3);
//set Windows tab as default (zero based)
tabHost.setCurrentTab(2);
}
}
但每当我运行应用程序时，它会启动第一个完成所有操作的活动，但如果您正确登录该应用程序就会停止。没有错误，这里是清单：
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.example.loginscreen"
android:versionCode="1"
android:versionName="1.0" >
<uses-sdk
android:minSdkVersion="10"
android:targetSdkVersion="17" />
<application
android:allowBackup="true"
android:icon="@drawable/ic_launcher"
android:label="@string/app_name"
android:theme="@style/AppTheme" >
<activity
android:name="com.example.loginscreen.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=".HomePage" />
<activity android:name=".HomePage2" />
<activity android:name=".HomePage3" />
</application>
</manifest>
这是主页面的xml：
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
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" >
<EditText
android:id="@+id/editText1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignBottom="@+id/textView2"
android:layout_marginLeft="32dp"
android:layout_toRightOf="@+id/textView2"
android:ems="10"
tools:ignore="TextFields" >
<requestFocus />
</EditText>
<EditText
android:id="@+id/editText2"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignBottom="@+id/textView3"
android:layout_alignLeft="@+id/editText1"
android:ems="10"
android:inputType="textPassword" />
<TextView
android:id="@+id/textView3"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_below="@+id/textView2"
android:layout_marginTop="40dp"
android:layout_toLeftOf="@+id/editText1"
android:hint="Password"
android:text="@string/password"
android:textAppearance="?android:attr/textAppearanceMedium" />
<TextView
android:id="@+id/textView5"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignBaseline="@+id/textView4"
android:layout_alignBottom="@+id/textView4"
android:layout_alignLeft="@+id/button1"
android:text="TextView"
tools:ignore="HardcodedText" />
<TextView
android:id="@+id/textView2"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignLeft="@+id/textView4"
android:layout_alignParentTop="true"
android:layout_marginTop="155dp"
android:hint="Username"
android:text="@string/username"
android:textAppearance="?android:attr/textAppearanceMedium" />
<ImageView
android:id="@+id/imageView1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_above="@+id/textView3"
android:layout_alignLeft="@+id/textView2"
android:layout_alignParentTop="true"
android:src="@drawable/tranzlogo1" />
<TextView
android:id="@+id/textView4"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_below="@+id/textView3"
android:layout_marginTop="26dp"
android:layout_toLeftOf="@+id/textView5"
android:text="@string/attempts"
android:textAppearance="?android:attr/textAppearanceMedium" />
<ProgressBar
android:id="@+id/progressBar1"
style="?android:attr/progressBarStyleHorizontal"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignLeft="@+id/textView4"
android:layout_alignRight="@+id/editText2"
android:layout_below="@+id/textView4" />
<Button
android:id="@+id/button1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentBottom="true"
android:layout_centerHorizontal="true"
android:layout_marginBottom="36dp"
android:onClick="login"
android:text="@string/Login" />
</RelativeLayout>
标签布局的链接页面：
<?xml version="1.0" encoding="utf-8"?>
<TabHost xmlns:android="http://schemas.android.com/apk/res/android"
android:id="@android:id/tabhost"
android:layout_width="fill_parent"
android:layout_height="fill_parent">
<LinearLayout
android:orientation="vertical"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:padding="5dp">
<TabWidget
android:id="@android:id/tabs"
android:layout_width="fill_parent"
android:layout_height="wrap_content" />
<FrameLayout
android:id="@android:id/tabcontent"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:padding="5dp" />
</LinearLayout>
</TabHost>
logcat的：
06-19 16:25:04.175: E/AndroidRuntime(16791): FATAL EXCEPTION: main
06-19 16:25:04.175: E/AndroidRuntime(16791): java.lang.IllegalStateException: Could not execute method of the activity
06-19 16:25:04.175: E/AndroidRuntime(16791): at android.view.View$1.onClick(View.java:3603)
06-19 16:25:04.175: E/AndroidRuntime(16791): at android.view.View.performClick(View.java:4103)
06-19 16:25:04.175: E/AndroidRuntime(16791): at android.view.View$PerformClick.run(View.java:17117)
06-19 16:25:04.175: E/AndroidRuntime(16791): at android.os.Handler.handleCallback(Handler.java:615)
06-19 16:25:04.175: E/AndroidRuntime(16791): at android.os.Handler.dispatchMessage(Handler.java:92)
06-19 16:25:04.175: E/AndroidRuntime(16791): at android.os.Looper.loop(Looper.java:137)
06-19 16:25:04.175: E/AndroidRuntime(16791): at android.app.ActivityThread.main(ActivityThread.java:4744)
06-19 16:25:04.175: E/AndroidRuntime(16791): at java.lang.reflect.Method.invokeNative(Native Method)
06-19 16:25:04.175: E/AndroidRuntime(16791): at java.lang.reflect.Method.invoke(Method.java:511)
06-19 16:25:04.175: E/AndroidRuntime(16791): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:786)
06-19 16:25:04.175: E/AndroidRuntime(16791): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
06-19 16:25:04.175: E/AndroidRuntime(16791): at dalvik.system.NativeStart.main(Native Method)
06-19 16:25:04.175: E/AndroidRuntime(16791): Caused by: java.lang.reflect.InvocationTargetException
06-19 16:25:04.175: E/AndroidRuntime(16791): at java.lang.reflect.Method.invokeNative(Native Method)
06-19 16:25:04.175: E/AndroidRuntime(16791): at java.lang.reflect.Method.invoke(Method.java:511)
06-19 16:25:04.175: E/AndroidRuntime(16791): at android.view.View$1.onClick(View.java:3598)
06-19 16:25:04.175: E/AndroidRuntime(16791): ... 11 more
06-19 16:25:04.175: E/AndroidRuntime(16791): Caused by: android.content.ActivityNotFoundException: Unable to find explicit activity class {com.example.loginscreen/com.example.loginscreen.LinkTabs}; have you declared this activity in your AndroidManifest.xml?
06-19 16:25:04.175: E/AndroidRuntime(16791): at android.app.Instrumentation.checkStartActivityResult(Instrumentation.java:1541)
06-19 16:25:04.175: E/AndroidRuntime(16791): at android.app.Instrumentation.execStartActivity(Instrumentation.java:1416)
06-19 16:25:04.175: E/AndroidRuntime(16791): at android.app.Activity.startActivityForResult(Activity.java:3351)
06-19 16:25:04.175: E/AndroidRuntime(16791): at android.app.Activity.startActivityForResult(Activity.java:3312)
06-19 16:25:04.175: E/AndroidRuntime(16791): at android.app.Activity.startActivity(Activity.java:3522)
06-19 16:25:04.175: E/AndroidRuntime(16791): at android.app.Activity.startActivity(Activity.java:3490)
06-19 16:25:04.175: E/AndroidRuntime(16791): at com.example.loginscreen.MainActivity.login(MainActivity.java:40)
06-19 16:25:04.175: E/AndroidRuntime(16791): ... 14 more
答案 0 :(得分：2)
您的错误消息是：
Unable to find explicit activity class {com.example.loginscreen/com.example.loginscreen.LinkTabs}; have you declared this activity in your AndroidManifest.xml?
该问题的答案显而易见：您的清单中没有<activity name=".LinkTabs"/>标记。只需添加它就可以了。