Создать настраиваемое представление и Добавить в XML

Question

Я создал обычай View, который рисует линию:

public class DrawView extends View { 
    Paint paint = new Paint(); 

    public DrawView(Context context) { 
     super(context); 
     paint.setColor(Color.BLACK); 
    } 

    @Override 
    public void onDraw(Canvas canvas) { 
     canvas.drawLine(0, 0, 100, 100, paint); 
    } 

} 

У меня есть MainActivity класс и activity_main макет, в котором мой макет содержит изображение и несколько кнопок. Я хочу поместить пользовательское представление, которое я создал в свой XML-файл (activity_main), где линия будет нарисована поверх изображения.

Я пытался добавить его:

<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" 
tools:context=".MainActivity"> 

//imageview and buttons here 

<com.myapp.alphasickbro.myapplication2.DrawView 
    android:id="@+id/paintView" 
    android:layout_width="100dp" 
    android:layout_height="100dp" 
    /> 

</RelativeLayout> 

Вот мой MainActivity:

public class MainActivity extends Activity { 

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

} 

Но когда я запускаю его, приложение, к сожалению, останавливается. Я что-то пропустил? Какие строки кода я должен добавить?

Любой ответ был бы оценен

EDIT:

04-18 15:24:47.517 26732-26732/com.myapp.alphasickbro.myapplication2 E/AndroidRuntime﹕ FATAL EXCEPTION: main 
    Process: com.myapp.alphasickbro.myapplication2, PID: 26732 
    java.lang.RuntimeException: Unable to start activity ComponentInfo{com.myapp.alphasickbro.myapplication2/com.myapp.alphasickbro.myapplication2.MainActivity}: android.view.InflateException: Binary XML file line #6: Error inflating class com.myapp.alphasickbro.myapplication2.DrawView 
      at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2318) 
      at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2396) 
      at android.app.ActivityThread.access$800(ActivityThread.java:139) 
      at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1293) 
      at android.os.Handler.dispatchMessage(Handler.java:102) 
      at android.os.Looper.loop(Looper.java:149) 
      at android.app.ActivityThread.main(ActivityThread.java:5268) 
      at java.lang.reflect.Method.invokeNative(Native Method) 
      at java.lang.reflect.Method.invoke(Method.java:515) 
      at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793) 
      at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:609) 
      at dalvik.system.NativeStart.main(Native Method) 
    Caused by: android.view.InflateException: Binary XML file line #6: Error inflating class com.myapp.alphasickbro.myapplication2.DrawView 
      at android.view.LayoutInflater.createView(LayoutInflater.java:620) 
      at android.view.LayoutInflater.createViewFromTag(LayoutInflater.java:696) 
      at android.view.LayoutInflater.rInflate(LayoutInflater.java:755) 
      at android.view.LayoutInflater.inflate(LayoutInflater.java:492) 
      at android.view.LayoutInflater.inflate(LayoutInflater.java:397) 
      at android.view.LayoutInflater.inflate(LayoutInflater.java:353) 
      at com.android.internal.policy.impl.PhoneWindow.setContentView(PhoneWindow.java:290) 
      at android.app.Activity.setContentView(Activity.java:2002) 
      at com.myapp.alphasickbro.myapplication2.MainActivity.onCreate(MainActivity.java:15) 
      at android.app.Activity.performCreate(Activity.java:5411) 
      at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1087) 
      at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2270) 
            at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2396) 
            at android.app.ActivityThread.access$800(ActivityThread.java:139) 
            at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1293) 
            at android.os.Handler.dispatchMessage(Handler.java:102) 
            at android.os.Looper.loop(Looper.java:149) 
            at android.app.ActivityThread.main(ActivityThread.java:5268) 
            at java.lang.reflect.Method.invokeNative(Native Method) 
            at java.lang.reflect.Method.invoke(Method.java:515) 
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793) 
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:609) 
            at dalvik.system.NativeStart.main(Native Method) 
    Caused by: java.lang.reflect.InvocationTargetException 
      at java.lang.reflect.Constructor.constructNative(Native Method) 
      at java.lang.reflect.Constructor.newInstance(Constructor.java:423) 
      at android.view.LayoutInflater.createView(LayoutInflater.java:594) 
            at android.view.LayoutInflater.createViewFromTag(LayoutInflater.java:696) 
            at android.view.LayoutInflater.rInflate(LayoutInflater.java:755) 
            at android.view.LayoutInflater.inflate(LayoutInflater.java:492) 
            at android.view.LayoutInflater.inflate(LayoutInflater.java:397) 
            at android.view.LayoutInflater.inflate(LayoutInflater.java:353) 
            at com.android.internal.policy.impl.PhoneWindow.setContentView(PhoneWindow.java:290) 
            at android.app.Activity.setContentView(Activity.java:2002) 
            at com.myapp.alphasickbro.myapplication2.MainActivity.onCreate(MainActivity.java:15) 
            at android.app.Activity.performCreate(Activity.java:5411) 
            at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1087) 
            at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2270) 
            at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2396) 
            at android.app.ActivityThread.access$800(ActivityThread.java:139) 
            at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1293) 
            at android.os.Handler.dispatchMessage(Handler.java:102) 
            at android.os.Looper.loop(Looper.java:149) 
            at android.app.ActivityThread.main(ActivityThread.java:5268) 
            at java.lang.reflect.Method.invokeNative(Native Method) 
            at java.lang.reflect.Method.invoke(Method.java:515) 
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793) 
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:609) 
            at dalvik.system.NativeStart.main(Native Method) 
    Caused by: java.lang.NullPointerException 
      at com.myapp.alphasickbro.myapplication2.DrawView.<init>(DrawView.java:27) 
            at java.lang.reflect.Constructor.constructNative(Native Method) 
            at java.lang.reflect.Constructor.newInstance(Constructor.java:423) 
            at android.view.LayoutInflater.createView(LayoutInflater.java:594) 
            at android.view.LayoutInflater.createViewFromTag(LayoutInflater.java:696) 
            at android.view.LayoutInflater.rInflate(LayoutInflater.java:755) 
            at android.view.LayoutInflater.inflate(LayoutInflater.java:492) 
            at android.view.LayoutInflater.inflate(LayoutInflater.java:397) 
            at android.view.LayoutInflater.inflate(LayoutInflater.java:353) 
            at com.android.internal.policy.impl.PhoneWindow.setContentView(PhoneWindow.java:290) 
            at android.app.Activity.setContentView(Activity.java:2002) 
            at com.myapp.alphasickbro.myapplication2.MainActivity.onCreate(MainActivity.java:15) 
            at android.app.Activity.performCreate(Activity.java:5411) 
            at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1087) 
            at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2270) 
            at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2396) 
            at android.app.ActivityThread.access$800(ActivityThread.java:139) 
            at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1293) 
            at android.os.Handler.dispatchMessage(Handler.java:102) 
            at android.os.Looper.loop(Looper.java:149) 
            at android.app.ActivityThread.main(ActivityThread.java:5268) 
            at java.lang.reflect.Method.invokeNative(Native Method) 
            at java.lang.reflect.Method.invoke(Method.java:515) 
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793) 
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:609) 
            at dalvik.system.NativeStart.main(Native Method) 

Answer 1

Я думаю, вам нужно добавить недостающие конструкторами. Очистите свой проект.

public class DrawView extends View { 

    Paint paint; 

    public DrawView(Context context) { 
     super(context); 
     init(); 
    } 

    public DrawView(Context context, AttributeSet attrs) { 
     super(context, attrs); 
     init(); 

    } 

    public DrawView(Context context, AttributeSet attrs, int defStyle) { 
     super(context, attrs, defStyle); 
     init(); 
    } 

    private void init() { 
     paint = new Paint(); 
     paint.setColor(Color.BLACK); 
    } 
}