Question

我已经阅读了许多关于开发Android应用程序的“常见”问题的主题。我也注意到这一切都取决于各种问题，一些来自清单，一些来自Java类。

我会在这里粘贴我的代码，如果有人看到奇怪的东西，请告诉我。

如您所见，我正在使用MVC模式。请告诉我你是否需要Model＆amp;控制器java类也是如此。

----- ENTER VIEW JAVA CLASS -----

    package kalle.jack.gui_tictactoe_android;

    import android.os.Bundle;
    import android.app.Activity;
    import android.view.Menu;
    import android.widget.Button;
    import android.widget.TextView;

    public class EnterView extends Activity {

private Model _model;
private Controller _controller;

public EnterView (Model aModel, Controller aController) {

    _model = aModel;
    _controller = aController;

}

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_enter_view);
}

@Override
public boolean onCreateOptionsMenu(Menu menu) {
    // Inflate the menu; this adds items to the action bar if it is present.
    getMenuInflater().inflate(R.menu.enter_view, menu);
    return true;
}

public void startClicked () {

    TextView s =  (TextView) findViewById(R.id.text1);
    String player1 = (String) s.getText();

    TextView t =  (TextView) findViewById(R.id.text2);
    String player2 = (String) t.getText();

    Button b = (Button) findViewById(R.id.button1);
    b.setId(10);
    int a = b.getId();

    _controller.setNames(player1, player2);
    _controller.buttonClicked(a);


}

 }

------ XML MANIFEST -------

 <?xml version="1.0" encoding="utf-8"?>
 <manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="kalle.jack.gui_tictactoe_android"
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"
    android:debuggable="true">
    <activity
        android:name="kalle.jack.gui_tictactoe_android.EnterView"
        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="kalle.jack.gui_tictactoe_android.PlayView"
        android:label="@string/title_activity_play_view" >
    </activity>
</application>

</manifest>

---------- XML activity_enter_view -----------

<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=".EnterView" >

<TextView
    android:id="@+id/textView1"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_alignParentTop="true"
    android:layout_centerHorizontal="true"
    android:layout_marginTop="49dp"
    android:text="Enter your names below..."
    android:textAppearance="?android:attr/textAppearanceLarge" />

<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="85dp"
    android:text="Start Game"
    android:onClick="startClicked"/>

<EditText
    android:id="@+id/text1"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_below="@+id/textView1"
    android:layout_centerHorizontal="true"
    android:layout_marginTop="42dp"
    android:ems="10"
    android:inputType="textPersonName"
    android:text="Player 1" />

<EditText
    android:id="@+id/text2"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_centerHorizontal="true"
    android:layout_centerVertical="true"
    android:ems="10"
    android:inputType="textPersonName"
    android:text="Player 2" >

    <requestFocus />
</EditText>

</RelativeLayout>

-----来自LOGCAT --------

05-26 06:33:24.460: E/AndroidRuntime(943): FATAL EXCEPTION: main
05-26 06:33:24.460: E/AndroidRuntime(943): java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{kalle.jack.gui_tictactoe_android/kalle.jack.gui_tictactoe_android.EnterView}: java.lang.InstantiationException: can't instantiate class kalle.jack.gui_tictactoe_android.EnterView; no empty constructor
05-26 06:33:24.460: E/AndroidRuntime(943):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2106)
05-26 06:33:24.460: E/AndroidRuntime(943):  at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2230)
05-26 06:33:24.460: E/AndroidRuntime(943):  at android.app.ActivityThread.access$600(ActivityThread.java:141)
05-26 06:33:24.460: E/AndroidRuntime(943):  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1234)
05-26 06:33:24.460: E/AndroidRuntime(943):  at android.os.Handler.dispatchMessage(Handler.java:99)
05-26 06:33:24.460: E/AndroidRuntime(943):  at android.os.Looper.loop(Looper.java:137)
05-26 06:33:24.460: E/AndroidRuntime(943):  at android.app.ActivityThread.main(ActivityThread.java:5041)
05-26 06:33:24.460: E/AndroidRuntime(943):  at java.lang.reflect.Method.invokeNative(Native Method)
05-26 06:33:24.460: E/AndroidRuntime(943):  at java.lang.reflect.Method.invoke(Method.java:511)
05-26 06:33:24.460: E/AndroidRuntime(943):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793)
05-26 06:33:24.460: E/AndroidRuntime(943):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560)
05-26 06:33:24.460: E/AndroidRuntime(943):  at dalvik.system.NativeStart.main(Native Method)
05-26 06:33:24.460: E/AndroidRuntime(943): Caused by: java.lang.InstantiationException: can't instantiate class kalle.jack.gui_tictactoe_android.EnterView; no empty constructor
05-26 06:33:24.460: E/AndroidRuntime(943):  at java.lang.Class.newInstanceImpl(Native Method)
05-26 06:33:24.460: E/AndroidRuntime(943):  at java.lang.Class.newInstance(Class.java:1319)
05-26 06:33:24.460: E/AndroidRuntime(943):  at android.app.Instrumentation.newActivity(Instrumentation.java:1054)
05-26 06:33:24.460: E/AndroidRuntime(943):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2097)
05-26 06:33:24.460: E/AndroidRuntime(943):  ... 11 more

Answer 1

首先，活动必须有空构造函数。如果需要参数，系统无法调用或实例化您的活动。删除参数或根本不定义构造函数。

卸下：

public EnterView (Model aModel, Controller aController) {
    _model = aModel;
    _controller = aController;
}

您将遇到的下一个错误是startClicked()方法，正如praveenLal所说。它应该接受View参数，该参数将代表调用方法时单击的按钮。

Answer 2

请使用public void startClicked（View v）{ ........ .... }

而不是public void startClicked（）。

不幸的是应用程序停止了（第一次活动）

2 个答案: