skeletonactivity.java

Google s android SDK

/* 
 * Copyright (C) 2007 Google Inc.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.google.android.skeletonapp;

import android.app.Activity;
import android.os.Bundle;
import android.view.KeyEvent;
import android.view.Menu;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.EditText;

/**
 * This class provides a basic demonstration of how to write an Android
 * activity. Inside of its window, it places a single view: an EditText that
 * displays and edits some internal text.
 */
class SkeletonActivity extends Activity {
    
    static final private int BACK_ID = Menu.FIRST;
    static final private int CLEAR_ID = Menu.FIRST + 1;

    private EditText mEditor;
    
    public SkeletonActivity() {
    }

    /** Called with the activity is first created. */
    @Override
    public void onCreate(Bundle icicle) {
        super.onCreate(icicle);

        // Inflate our UI from its XML layout description.
        setContentView(R.layout.skeleton_activity);

        // Find the text editor view inside the layout, because we
        // want to do various programmatic things with it.
        mEditor = (EditText) findViewById(R.id.editor);

        // Hook up button presses to the appropriate event handler.
        ((Button) findViewById(R.id.back)).setOnClickListener(mBackListener);
        ((Button) findViewById(R.id.clear)).setOnClickListener(mClearListener);
        
        // There are two cases we are interested in here: If icicle
        // is supplied, we need to place it into the text editor to
        // put us back to that state. Otherwise, we need to initialize
        // the text editor to its default state.
        Bundle textState = icicle != null ? icicle.getBundle("text") : null;

        // Note that this example is a little different than what is common
        // in a "real" application, where the data being edited is stored
        // in some persistent back-end content provider. Here we save and
        // restore all of the text editor state, including the text itself.
        // If the text was kept in persistent storage, we would instead load
        // the text from storage and restoreState() would only restore
        // the normal editor state (cursor position etc).

        // If we have state, try to restore it; if we don't have state
        // or the restore fails, initialize to default state.
        if (textState == null || !mEditor.restoreState(textState)) {
            mEditor.setText(getText(R.string.main_label));
        }
    }

    /**
     * Called when the activity is about to start interacting with the user.
     */
    @Override
    protected void onResume() {
        super.onResume();
    }

    /**
     * Called to remember the current state before the activity stops.
     */
    @Override
    protected void onFreeze(Bundle outState) {
        super.onFreeze(outState);

        // Save the current text editor state. As noted above in
        // onCreate(), this is somewhat unusual in that our text
        // is not in persistent storage. If we did have it in persistent
        // storage, we would call mEditor.saveState() here instead.
        outState.putBundle("text", mEditor.saveStateAndText());
    }

    /**
     * Called when your activity's options menu needs to be created.
     */
    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        super.onCreateOptionsMenu(menu);

        // We are going to create two menus. Note that we assign them
        // unique integer IDs, labels from our string resources, and
        // given them shortcuts.
        menu.add(0, BACK_ID, R.string.back).
            setShortcut(KeyEvent.KEYCODE_0, 0, KeyEvent.KEYCODE_B);
        menu.add(0, CLEAR_ID, R.string.clear).
            setShortcut(KeyEvent.KEYCODE_1, 0, KeyEvent.KEYCODE_C);

        return true;
    }

    /**
     * Called right before your activity's option menu is displayed.
     */
    @Override
    public boolean onPrepareOptionsMenu(Menu menu) {
        super.onPrepareOptionsMenu(menu);

        // Before showing the menu, we need to decide whether the clear
        // item is enabled depending on whether there is text to clear.
        menu.setItemShown(CLEAR_ID, mEditor.getText().length() > 0);

        return true;
    }

    /**
     * Called when a menu item is selected.
     */
    @Override
    public boolean onOptionsItemSelected(Menu.Item item) {
        switch (item.getId()) {
        case BACK_ID:
            finish();
            return true;
        case CLEAR_ID:
            mEditor.setText("");
            return true;
        }

        return super.onOptionsItemSelected(item);
    }

    /**
     * A call-back for when the user presses the back button.
     */
    OnClickListener mBackListener = new OnClickListener() {
        public void onClick(View v) {
            finish();
        }
    };

    /**
     * A call-back for when the user presses the clear button.
     */
    OnClickListener mClearListener = new OnClickListener() {
        public void onClick(View v) {
            mEditor.setText("");
        }
    };
}