自定义键盘抛出异常

Question

I have a simple enough idea, which is to make a custom keyboard instead of using the built in keyboard to avoid autocorrect, symbols, numbers, etc. which I don't want in my app. For some reason, when I call the event typeKey to "type" a letter, the event calling itself throws an exception.

Here is the java code:

public class MainActivity extends Activity {

    Vector<String> answer = new Vector<String>(1,1);
    int ansLength = 1;
    private TextView answerbox;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        answerbox = (TextView) findViewById(R.id.answerbox);
        setContentView(R.layout.activity_main);

    }

    @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;
    }


    public void typeKey(Object sender)
    {
        Button pressed = (Button) sender;
        answer.add(ansLength, (String) pressed.getText());
        ansLength++;
        answerbox.setText((CharSequence) answer);
    }
}

Here is the relevant XML:

<Button
            android:id="@+id/q"
            style="?android:attr/buttonStyleSmall"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_alignParentTop="true"
            android:text="Q"
            android:onClick="typeKey"/>
<TextView
        android:id="@+id/answerbox"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_x="43dp"
        android:layout_y="40dp"
        android:text="Large Text"
        android:textAppearance="?android:attr/textAppearanceLarge" />

The goal is to be able to type and have the typed text show up as the textview. My thought to do this was to add to every key an event, typeKey, which would get the text from whatever button called the event, add it to the vector "answer", and then set the textview to display the text of "answer".

Here is the whole stack trace:

08-06 13:04:49.497: E/AndroidRuntime(15224): FATAL EXCEPTION: main
08-06 13:04:49.497: E/AndroidRuntime(15224): java.lang.IllegalStateException: Could not execute method of the activity
08-06 13:04:49.497: E/AndroidRuntime(15224):    at android.view.View$1.onClick(View.java:3698)
08-06 13:04:49.497: E/AndroidRuntime(15224):    at android.view.View.performClick(View.java:4222)
08-06 13:04:49.497: E/AndroidRuntime(15224):    at android.view.View$PerformClick.run(View.java:17273)
08-06 13:04:49.497: E/AndroidRuntime(15224):    at android.os.Handler.handleCallback(Handler.java:615)
08-06 13:04:49.497: E/AndroidRuntime(15224):    at android.os.Handler.dispatchMessage(Handler.java:92)
08-06 13:04:49.497: E/AndroidRuntime(15224):    at android.os.Looper.loop(Looper.java:137)
08-06 13:04:49.497: E/AndroidRuntime(15224):    at android.app.ActivityThread.main(ActivityThread.java:4895)
08-06 13:04:49.497: E/AndroidRuntime(15224):    at java.lang.reflect.Method.invokeNative(Native Method)
08-06 13:04:49.497: E/AndroidRuntime(15224):    at java.lang.reflect.Method.invoke(Method.java:511)
08-06 13:04:49.497: E/AndroidRuntime(15224):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:994)
08-06 13:04:49.497: E/AndroidRuntime(15224):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:761)
08-06 13:04:49.497: E/AndroidRuntime(15224):    at dalvik.system.NativeStart.main(Native Method)
08-06 13:04:49.497: E/AndroidRuntime(15224): Caused by: java.lang.reflect.InvocationTargetException
08-06 13:04:49.497: E/AndroidRuntime(15224):    at java.lang.reflect.Method.invokeNative(Native Method)
08-06 13:04:49.497: E/AndroidRuntime(15224):    at java.lang.reflect.Method.invoke(Method.java:511)
08-06 13:04:49.497: E/AndroidRuntime(15224):    at android.view.View$1.onClick(View.java:3693)
08-06 13:04:49.497: E/AndroidRuntime(15224):    ... 11 more
08-06 13:04:49.497: E/AndroidRuntime(15224): Caused by: java.lang.ClassCastException: java.util.Vector cannot be cast to java.lang.CharSequence
08-06 13:04:49.497: E/AndroidRuntime(15224):    at gguday.lexiconicmkii.MainActivity.typeKey(MainActivity.java:42)
08-06 13:04:49.497: E/AndroidRuntime(15224):    ... 14 more

Thanks in advance for any help.

Answer 1

Three issues:

You are trying to search for your answerbox view before you call setContentView(R.layout.activity_main) . This will always result in answerbox being null since there are no views available (yet) and throw a NullPointerException when you try to access answerbox . Make sure to switch the order and search for answerbox after you call setContentView(R.layout.activity_main)

Ex.

setContentView(R.layout.activity_main);
answerbox = (TextView) findViewById(R.id.answerbox);

Second, change your click method to take a View as the parameter (instead of Object ) as onClick methods expect this.. Although, I think what you have should be ok since a View technically is an object and you are casting it to the appropriate type. I'm not sure how picky it is when trying to call the click listener so for safety I'd just change it to View . Ex.

public void typeKey(View sender)
{
        Button pressed = (Button) sender;
        answer.add(ansLength, (String) pressed.getText());
        ansLength++;
        answerbox.setText((CharSequence) answer);
}

Lastly,

You cannot simply cast your vector to a CharSequence. If you wish to make a string out of it you will have to loop through each value and add it to a larger string.. Ex.

public void typeKey(View sender)
{
    Button pressed = (Button) sender;
    answer.add(ansLength, (String) pressed.getText());
    ansLength++;


    StringBuilder stringBuilder = new StringBuilder();
    for (String string : answer) {
        stringBuilder.append(string);
    }

    answerbox.setText(stringBuilder.toString());
}

You should also start your ansLength at 0 since the vectors are zero indexed.

int ansLength = 1;