onclick出错

Question

我希望在点击按钮时引导活动。但是我的应用程序崩溃了。

这是我的代码，其中指出了错误（startActivity(intent);），

Button ExerciseButton = (Button)findViewById(R.id.button3);

   ExerciseButton.setOnClickListener(new View.OnClickListener() {

       @Override
      public void onClick(View view) {
        Intent intent = new Intent(MainActivity.this, Database.class);
        startActivity(intent);
      }

    });

按钮的xml

                <Button
                android:id="@+id/button3"
                android:layout_width="110dp"
                android:layout_height="50dp"
                android:background="@drawable/button"
                android:onClick="grammar"
                android:text="@string/button_exercise"
                android:layout_marginTop="15dp"
                android:layout_marginBottom="15dp"
                android:layout_marginLeft="28dp" />

这是一个名为

的活动

public class Database extends Activity  {
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);


             try {
        String destPath = "/data/data/" + getPackageName()
                + "/databases/questions";
        File f = new File(destPath);
        if (!f.exists()) {
            CopyDB(getBaseContext().getAssets().open("questions"),
                    new FileOutputStream(destPath));
        }
    } 

             catch (FileNotFoundException e) {
        e.printStackTrace();
        Toast.makeText(Database.this, "Error File", Toast.LENGTH_SHORT)
                .show(); 
    } 
             catch (IOException e1) {
        e1.printStackTrace();
       Toast.makeText(Database.this, "Error IO", Toast.LENGTH_SHORT)
                .show();
    }


        DatabaseHandler db = new DatabaseHandler(this);


        long id = db.addQuestion("Question1", "answer1", "answer2", "answer3", "answer4", "answer");
        //id = db.addQuestion("Question2", "answer2");
        db.close();



       Cursor cursor = db.getAllQuestions();
        if (cursor.moveToFirst())
        {
            do {
                DisplayRecord(cursor);

            }
            while(cursor.moveToNext());
        }

        db.close();
    }

        public void CopyDB(InputStream inputstream, OutputStream outputstream)        
                throws IOException {
            byte[] buffer = new byte[1024];
            int length;
            while ((length = inputstream.read(buffer))>0){
                outputstream.write(buffer, 0, length);
            }
            inputstream.close();
            outputstream.close();
        }

        public void DisplayRecord(Cursor cursor){
            Toast.makeText(this,
                    "id:" + cursor.getString(0) + "\n" +
                    "Question:" + cursor.getString(1) + "\n" +
                    "Answer1:" + cursor.getString(2) + "\n" +
"Answer2:" + cursor.getString(3) + "\n" +
"Answer3:" + cursor.getString(4) + "\n" +
"Answer4:" + cursor.getString(5) + "\n" +
"Answer:" + cursor.getString(6),
                    Toast.LENGTH_SHORT).show();
        }

     }

logcat在下面。

02-27 10:35:41.061: W/KeyCharacterMap(11469): No keyboard for id 0
02-27 10:35:41.061: W/KeyCharacterMap(11469): Using default keymap: /system/usr/keychars/qwerty.kcm.bin
02-27 10:35:42.471: D/AndroidRuntime(11469): Shutting down VM
02-27 10:35:42.481: W/dalvikvm(11469): threadid=1: thread exiting with uncaught exception (group=0x40015560)
02-27 10:35:42.491: E/AndroidRuntime(11469): FATAL EXCEPTION: main
02-27 10:35:42.491: E/AndroidRuntime(11469): android.content.ActivityNotFoundException: Unable to find explicit activity class {com.example.grammer/com.example.grammer.Database}; have you declared this activity in your AndroidManifest.xml?
02-27 10:35:42.491: E/AndroidRuntime(11469):    at android.app.Instrumentation.checkStartActivityResult(Instrumentation.java:1405)
02-27 10:35:42.491: E/AndroidRuntime(11469):    at android.app.Instrumentation.execStartActivity(Instrumentation.java:1379)
02-27 10:35:42.491: E/AndroidRuntime(11469):    at android.app.Activity.startActivityForResult(Activity.java:2827)
02-27 10:35:42.491: E/AndroidRuntime(11469):    at android.app.Activity.startActivity(Activity.java:2933)
02-27 10:35:42.491: E/AndroidRuntime(11469):    at com.example.grammer.MainActivity$2.onClick(MainActivity.java:43)
02-27 10:35:42.491: E/AndroidRuntime(11469):    at android.view.View.performClick(View.java:2485)
02-27 10:35:42.491: E/AndroidRuntime(11469):    at android.view.View$PerformClick.run(View.java:9080)
02-27 10:35:42.491: E/AndroidRuntime(11469):    at android.os.Handler.handleCallback(Handler.java:587)
02-27 10:35:42.491: E/AndroidRuntime(11469):    at android.os.Handler.dispatchMessage(Handler.java:92)
02-27 10:35:42.491: E/AndroidRuntime(11469):    at android.os.Looper.loop(Looper.java:123)
02-27 10:35:42.491: E/AndroidRuntime(11469):    at android.app.ActivityThread.main(ActivityThread.java:3683)
02-27 10:35:42.491: E/AndroidRuntime(11469):    at java.lang.reflect.Method.invokeNative(Native Method)
02-27 10:35:42.491: E/AndroidRuntime(11469):    at java.lang.reflect.Method.invoke(Method.java:507)
02-27 10:35:42.491: E/AndroidRuntime(11469):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:839)
02-27 10:35:42.491: E/AndroidRuntime(11469):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:597)
02-27 10:35:42.491: E/AndroidRuntime(11469):    at dalvik.system.NativeStart.main(Native Method)
02-27 10:35:44.961: I/Process(11469): Sending signal. PID: 11469 SIG: 9

Answer 1

将此添加到清单文件...

<activity android:name=".Database" />

Answer 2

你已经在Button小部件中设置了onclick =“grammer”属性，但在你的MainActivity中没有语法方法。可能你应该这样使用。

public void grammmer(View view)
{ 
    // To do your stuff  
 }

或

就像你将onclicklistener设置为

一样

 Button b1 = (Button)findViewById(R.id.YourButton);
b1.setonClickListener(new View.onClickListener(){
@Override
  public void onClick(View view) {
    Intent intent = new Intent(MainActivity.this, Database.class);
    startActivity(intent);
  }

 });

和btw，在AndroidManifest.xml中注册您的下一个活动

<activity name=".YourActivity" />

Answer 3

您没有将活动添加到清单中 - 这意味着您的应用无法识别您的活动。

  

必须在清单文件中声明所有活动，   AndroidManifest.xml，使用<activity>元素。

请详细了解，重要的是要知道：
http://developer.android.com/training/basics/firstapp/starting-activity.html
http://developer.android.com/guide/topics/manifest/activity-element.html

例如：

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="your.package.name">
 <uses-sdk android:minSdkVersion="18" />
    <application android:icon="@drawable/icon" android:label="@string/app_name">
        <activity android:name=".Activity1" android:label="@string/app_name"></activity>
        <activity android:name=".Activity2"></activity>
    </application>
    </manifest>

Answer 4

我认为问题可能出于以下问题......

1）在您设置Database.java的{​​{1}}中，您的班级名称为数据库，因此请确保您的XML名称正确无误。因为我认为你也有setContentView(R.layout.activity_main);所以要确保你有两个不同的XML用于这两个活动。并且您将正确的XML分配给正确的Java文件。

2）我认为你没有在main_activity.java文件中设置数据库名称，所以@Anil Bhatiya告诉你，这样做。

Answer 5

您已在xml中设置了android:onClick=grammar，因此您无需实现onclick侦听器。只需将方法名称创建为“语法”，并将您的意图放在该方法中