java – 使用自定义方法绘制到画布？
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我正在编写一个Android 2-D游戏,我遇到了一些麻烦.
目前,在我的包中,我有一个绘制画布实例的线程.我正在从资源中绘制Drawable位图.我想做的是让线程处理背景图像的绘制.但是,自定义对象的实例可以使用可绘制对象绘制到同一个画布.这在逻辑上似乎是可能的,但我无法让它工作.每当我尝试检索自定义类中的资源时,应用程序在启动时崩溃.
以下是我的一些努力:(如果我做了一些愚蠢的事情,请不要笑,我正在努力.)
public class Worker{
//Get drawables
// Resources res = getResources();
// Drawable man1 = res.getDrawable(R.drawable.workertest);
// Context mContext;
// Resources res = mContext.getResources();
// Drawable man1 = mContext.getResources().getDrawable(R.drawable.workertest);
// Drawable man2 = mContext.getResources().getDrawable(R.drawable.workertest1);
// Drawable man1 = res.getDrawable(R.drawable.workertest);
// Drawable man2 = res.getDrawable(R.drawable.workertest1);
}
正如你所看到的,我尝试了几种不同的方法,并且我也尝试过(扩展活动)添加到我的班级,但我无法弄清楚这一点.
这段代码并没有解决实际绘制到画布的问题,我还没有跨过那座桥
编辑：这是活动.如你所见,它在月球视图中调用一个线程.该线程实例化需要检索Drawable的对象.如何以神的名义获取对象的应用程序上下文？还是有其他办法吗？是的,这是来自android示例代码的代码.
public class LunarLander extends Activity {
private static final int MENU_EASY = 1;
private static final int MENU_HARD = 2;
private static final int MENU_MEDIUM = 3;
private static final int MENU_PAUSE = 4;
private static final int MENU_RESUME = 5;
private static final int MENU_START = 6;
private static final int MENU_STOP = 7;
/** A handle to the thread that's actually running the animation. */
public static LunarThread mLunarThread;
/** A handle to the View in which the game is running. */
public LunarView mLunarView;
/**
* Invoked during init to give the Activity a chance to set up its Menu.
*
* @param menu the Menu to which entries may be added
* @return true
*/
@Override
public boolean onCreateOptionsMenu(Menu menu) {
super.onCreateOptionsMenu(menu);
menu.add(0, MENU_START, 0, R.string.menu_start);
menu.add(0, MENU_STOP, 0, R.string.menu_stop);
menu.add(0, MENU_PAUSE, 0, R.string.menu_pause);
menu.add(0, MENU_RESUME, 0, R.string.menu_resume);
menu.add(0, MENU_EASY, 0, R.string.menu_easy);
menu.add(0, MENU_MEDIUM, 0, R.string.menu_medium);
menu.add(0, MENU_HARD, 0, R.string.menu_hard);
return true;
}
/**
* Invoked when the user selects an item from the Menu.
*
* @param item the Menu entry which was selected
* @return true if the Menu item was legit (and we consumed it), false
* otherwise
*/
@Override
public boolean onOptionsItemSelected(MenuItem item) {
switch (item.getItemId()) {
case MENU_START:
mLunarThread.doStart();
return true;
case MENU_STOP:
mLunarThread.setState(LunarThread.STATE_LOSE,
getText(R.string.message_stopped));
return true;
case MENU_PAUSE:
mLunarThread.pause();
return true;
case MENU_RESUME:
mLunarThread.unpause();
return true;
case MENU_EASY:
mLunarThread.setDifficulty(LunarThread.DIFFICULTY_EASY);
return true;
case MENU_MEDIUM:
mLunarThread.setDifficulty(LunarThread.DIFFICULTY_MEDIUM);
return true;
case MENU_HARD:
mLunarThread.setDifficulty(LunarThread.DIFFICULTY_HARD);
return true;
}
return false;
}
/**
* Invoked when the Activity is created.
*
* @param savedInstanceState a Bundle containing state saved from a previous
* execution, or null if this is a new execution
*/
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
// tell system to use the layout defined in our XML file
setContentView(R.layout.lunar_layout);
// get handles to the LunarView from XML, and its LunarThread
mLunarView = (LunarView) findViewById(R.id.lunar);
mLunarThread = mLunarView.getThread();
// give the LunarView a handle to the TextView used for messages
mLunarView.setTextView((TextView) findViewById(R.id.text));
if (savedInstanceState == null) {
// we were just launched: set up a new game
mLunarThread.setState(LunarThread.STATE_READY);
Log.w(this.getClass().getName(), "SIS is null");
} else {
// we are being restored: resume a previous game
mLunarThread.restoreState(savedInstanceState);
Log.w(this.getClass().getName(), "SIS is nonnull");
}
}
/**
* Invoked when the Activity loses user focus.
*/
@Override
protected void onPause() {
super.onPause();
mLunarView.getThread().pause(); // pause game when Activity pauses
}
/**
* Notification that something is about to happen, to give the Activity a
* chance to save state.
*
* @param outState a Bundle into which this Activity should save its state
*/
@Override
protected void onSaveInstanceState(Bundle outState) {
// just have the View's thread save its state into our Bundle
super.onSaveInstanceState(outState);
mLunarThread.saveState(outState);
Log.w(this.getClass().getName(), "SIS called");
}
public boolean onTouchEvent(MotionEvent event){
int clickX = Math.round(event.getX()/10)*10;
int clickY = Math.round(event.getY()/10)*10;
LunarView.xCo = clickX;
LunarView.yCo = clickY;
return true;
}
解决方法:
正如Greg建议的那样,问题在于获得正确的Context来检索资源.
解决此问题的一种简单方法是将主Activity作为参数传递给Worker类构造函数,并将其另存为私有Context字段.就像是：
public class Worker{
private Context mContext;
public Worker (Context context) {
mContext = context;
Resources res = mContext.getResources();
// all the rest of your code
}
}
您将在主要活动中使用它：
Worker worker = new Worker(this);
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