Question

I am new to Android and am trying to understand the compound view concept if android. I am not sure that my below implementation is practical or not but it is for learning purpose and i have taken this idea from Wrox Android book. So, i have three components i.e a button, a edit text and a list view. The purpose of edit text is to write some text, while the list gets updated with the text and the button is the clear button and it is suppose to clear the edit text. What i am planning to do is to keep the clear button and edit text in one view group. Below it the java and xml code for it.

public class CompoundView extends LinearLayout {

EditText editText;
Button clearButton;

public CompoundView (Context context, AttributeSet attr) {
    super(context, attr);
    String infService = Context.LAYOUT_INFLATER_SERVICE;
    LayoutInflater li;

    li = (LayoutInflater)getContext().getSystemService(infService);
    li.inflate(R.layout.clearable_edit_text, this, true);

    editText = (EditText) findViewById(R.id.editText);
    clearButton = (Button) findViewById(R.id.clearButton);

    hookUpButton ();
}

public void hookUpButton () {

    clearButton.setOnClickListener(new Button.OnClickListener () {
        public void onClick (View v) {
            editText.setText ("");

        }
    });
}

public EditText getEditText() {
    return this.editText;
}

}

XML

<?xml version="1.0" encoding="utf-8"?>
<merge xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="horizontal"
android:layout_width="match_parent"
android:layout_height="wrap_content">
<EditText 
    android:id="@+id/editText"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    />
<Button
    android:id="@+id/clearButton"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:text="Clear"
    />
</merge>

I have a strong feeling that this implementation is fine. In the next part I have the MainActivity.java and activity_main.xml. In this i am facing the problem and am most probably doing some thing wrong.

public class MainActivity extends Activity {

@SuppressLint({ "ParserError", "ParserError" })
public class MainActivity extends Activity {

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    ListView myListView = (ListView)findViewById(R.id.myListView);

    final CompoundView textAndClear = (CompoundView) findViewById(R.id.myEditAndClear) ;
    final EditText editText = textAndClear.getEditText();
    final ArrayList<String> toDoItems = new ArrayList<String>();

    final ArrayAdapter<String> aa;
    int resId = R.layout.todolist_item;
    aa= new ArrayAdapter<String> (this, resId, toDoItems);
    myListView.setAdapter(aa);

    editText.setOnKeyListener(new View.OnKeyListener() {

        public boolean onKey(View v, int keyCode, KeyEvent event) {
            if(event.getAction() == KeyEvent.ACTION_DOWN)
                if ((keyCode == KeyEvent.ACTION_DOWN) || (keyCode == KeyEvent.KEYCODE_ENTER)){
                    toDoItems.add(0,editText.getText().toString());
                    aa.notifyDataSetChanged();
                    editText.setText("");
                    return true;
                }
            return false;
        }
    });
    }
}

and the XML

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:orientation="vertical"
android:layout_width="match_parent"
android:layout_height="match_parent" >

<com.example.wroxexample.CompoundView
    android:id="@+id/myClearableEditText"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    />
<ListView
    android:id="@+id/myListView"
    android:layout_below="@+id/myEditText"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"/>
</RelativeLayout>

and the error is

06-29 06:32:11.783: E/AndroidRuntime(5413): FATAL EXCEPTION: main
06-29 06:32:11.783: E/AndroidRuntime(5413): java.lang.RuntimeException: Unable to start     activity ComponentInfo{com.example.wroxexample/com.example.wroxexample.MainActivity}: android.view.InflateException: Binary XML file line #8: Error inflating class com.example.wroxexmple.CompoundView
06-29 06:32:11.783: E/AndroidRuntime(5413):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1956)
06-29 06:32:11.783: E/AndroidRuntime(5413):     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1981)
06-29 06:32:11.783: E/AndroidRuntime(5413):     at android.app.ActivityThread.access$600(ActivityThread.java:123)
06-29 06:32:11.783: E/AndroidRuntime(5413):     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1147)
06-29 06:32:11.783: E/AndroidRuntime(5413):     at android.os.Handler.dispatchMessage(Handler.java:99)
06-29 06:32:11.783: E/AndroidRuntime(5413):     at android.os.Looper.loop(Looper.java:137)
06-29 06:32:11.783: E/AndroidRuntime(5413):     at android.app.ActivityThread.main(ActivityThread.java:4424)
06-29 06:32:11.783: E/AndroidRuntime(5413):     at java.lang.reflect.Method.invokeNative(Native Method)
06-29 06:32:11.783: E/AndroidRuntime(5413):     at java.lang.reflect.Method.invoke(Method.java:511)
06-29 06:32:11.783: E/AndroidRuntime(5413):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:784)
06-29 06:32:11.783: E/AndroidRuntime(5413):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:551)
06-29 06:32:11.783: E/AndroidRuntime(5413):     at dalvik.system.NativeStart.main(Native Method)
06-29 06:32:11.783: E/AndroidRuntime(5413): Caused by: android.view.InflateException: Binary XML file line #8: Error inflating class com.example.wroxexmple.CompoundView
06-29 06:32:11.783: E/AndroidRuntime(5413):     at android.view.LayoutInflater.createViewFromTag(LayoutInflater.java:691)
06-29 06:32:11.783: E/AndroidRuntime(5413):     at android.view.LayoutInflater.rInflate(LayoutInflater.java:739)
06-29 06:32:11.783: E/AndroidRuntime(5413):     at android.view.LayoutInflater.inflate(LayoutInflater.java:489)
06-29 06:32:11.783: E/AndroidRuntime(5413):     at android.view.LayoutInflater.inflate(LayoutInflater.java:396)
06-29 06:32:11.783: E/AndroidRuntime(5413):     at android.view.LayoutInflater.inflate(LayoutInflater.java:352)
06-29 06:32:11.783: E/AndroidRuntime(5413):     at com.android.internal.policy.impl.PhoneWindow.setContentView(PhoneWindow.java:251)
06-29 06:32:11.783: E/AndroidRuntime(5413):     at android.app.Activity.setContentView(Activity.java:1835)
06-29 06:32:11.783: E/AndroidRuntime(5413):     at com.example.wroxexample.MainActivity.onCreate(MainActivity.java:20)
06-29 06:32:11.783: E/AndroidRuntime(5413):     at android.app.Activity.performCreate(Activity.java:4465)
06-29 06:32:11.783: E/AndroidRuntime(5413):     at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1049)
06-29 06:32:11.783: E/AndroidRuntime(5413):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1920)
06-29 06:32:11.783: E/AndroidRuntime(5413):     ... 11 more
06-29 06:32:11.783: E/AndroidRuntime(5413): Caused by: java.lang.ClassNotFoundException: com.example.wroxexmple.CompoundView
06-29 06:32:11.783: E/AndroidRuntime(5413):     at dalvik.system.BaseDexClassLoader.findClass(BaseDexClassLoader.java:61)
06-29 06:32:11.783: E/AndroidRuntime(5413):     at java.lang.ClassLoader.loadClass(ClassLoader.java:501)
06-29 06:32:11.783: E/AndroidRuntime(5413):     at java.lang.ClassLoader.loadClass(ClassLoader.java:461)
06-29 06:32:11.783: E/AndroidRuntime(5413):     at android.view.LayoutInflater.createView(LayoutInflater.java:552)
06-29 06:32:11.783: E/AndroidRuntime(5413):     at android.view.LayoutInflater.createViewFromTag(LayoutInflater.java:680)
06-29 06:32:11.783: E/AndroidRuntime(5413):     ... 21 more

Answer 1

Below the error you posted should be the real cause for the exception. My guess, after a simple look at your code, is that the exception comes from the fact that you only implemented the constructor that takes a Context(this constructor would normally be used when you instantiate the View in code). As you use the compound view in a xml layout the constructor that also takes an AttributeSet will be used(instead of the one you implemented that only takes a Context).

Also, as a side note you search for your compound View in the onCreate method and you cast it to a LinearLayout. In the onKey callback you then try to call the getText() and setText() on it, methods which are not implemented for the class LinearLayout(you maybe had them in your custom view but if you cast the view as a LinearLayout the methods will not be available).

Also you might want to read on the merge tag to improve the layout for your compound View.