我有一个数据库，其中包含以下格式的记录：。我希望我的应用程序做的是从外部数据库中选择记录，并使用SurfaceView在手机屏幕上显示这些记录。
目前，我有一个Activity和一个负责应用程序记录收集部分的服务。活动将意图传递给服务，服务通过返回需要显示的记录来响应。记录作为Data类的实例存储在我的程序中，并且仅具有在视图中绘制元素的位置的屏幕坐标（我只是为DB中的每个记录绘制一个圆圈）。
为了简洁起见，我不会包含该服务，但我将包含Activity类的骨架和我希望显示的数据。
public class Data{
private int x;
private int y;
private int id;
private int shape;
/*
* Getters and setters for class properties
*/
}
public class Displayer extends Activity {
int ht;
int wt;
dataReceiver dreceiver;
public static Map<String, Data> Info;
private LinearLayout linear;
private static final int RADIUS = 20;
Panel panel;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
requestWindowFeature(Window.FEATURE_NO_TITLE);
panel=new Panel(this);
setContentView(panel);
Intent scv = new Intent(this, DataService.class);
startService(scv);
}
/*
* Various other methods to take care of onDestroy, onPause, etc.
*/
public class dataReceiver extends BroadcastReceiver {
//Get new data from intents sent by the Service and store it in Info variable
//Update the Testing Map data-structure in the Panel SurfaceView with new records
panel.setData(Info);
}
}
我遇到的问题与SurfaceView有关。我意识到很多人会建议我只使用常规View，但我的应用程序涉及很多元素，因此SurfaceView更适合我的需求。下面是我的SurfaceView类的框架，它包含一个用于管理线程的嵌套类。
public class Panel extends SurfaceView implements SurfaceHolder.Callback {
private PanelThread _thread;
private Paint circlepaint;
private Paint textpaint;
private static int CircleColor = Color.YELLOW;
private static int TextColor = Color.RED;
private static Map<String, Data> Testing;
public Panel(Context context, Map<String, Data> entries) {
super(context);
getHolder().addCallback(this);
_thread = new PanelThread(getHolder(), this);
setFocusable(true);
textpaint = new Paint(Paint.ANTI_ALIAS_FLAG);
textpaint.setStyle(Style.FILL_AND_STROKE);
textpaint.setColor(TextColor);
Testing = new HashMap<String, Data>();
// Log.d("TestingSize",String.valueOf(Testing.size()));
if (!(Testing.isEmpty())) {
Testing.clear();
}
for (Map.Entry<String, Data> e : entries.entrySet()) {
String keyvalue = e.getKey();
Data v = e.getValue();
Panel.Testing.put(keyvalue, v);
}
}
public Panel(Context context) {
super(context);
getHolder().addCallback(this);
_thread = new PanelThread(getHolder(), this);
setFocusable(true);
textpaint = new Paint(Paint.ANTI_ALIAS_FLAG);
textpaint.setStyle(Style.FILL_AND_STROKE);
textpaint.setColor(TextColor);
Testing = new HashMap<String, Victims>();
}
@Override
public void surfaceChanged(SurfaceHolder holder, int format, int width, int height) {
// TODO Auto-generated method stub
}
@Override
public void surfaceCreated(SurfaceHolder holder) {
_thread.setRunning(true);
_thread.start();
}
@Override
public void surfaceDestroyed(SurfaceHolder holder) {
/* we have to tell thread to shut down
* & wait for it to finish,
* or else it might touch the Surface
* after we return and explode
*/
boolean retry = true;
_thread.setRunning(false);
while (retry) {
try {
_thread.join();
retry = false;
} catch (InterruptedException e) {
// we will try it again and again...
}
}
}
/*If new records are received
* from the service, they can be updated
* using this method
*/
public void setData(Map<String,Data>Info){
Testing=Info;
}
/*
* Iterate over all contents of Testing List and display them to the screen
*/
@Override
public void onDraw(Canvas canvas) {
super.onDraw(canvas);
if (!(Testing.isEmpty())) {
for (Map.Entry<String, Victims> e : Testing.entrySet()) {
Data d = e.getValue();
canvas.drawCircle(d.getX(), d.getY(), 10, circlepaint);
}
}
canvas.save();
canvas.restore();
}
/*
* Nested class to manage the threads for the SurfaceView
*/
class PanelThread extends Thread {
private SurfaceHolder _surfaceHolder;
private Panel _panel;
private boolean _run = false;
public PanelThread(SurfaceHolder surfaceHolder, Panel panel) {
_surfaceHolder = surfaceHolder;
_panel = panel;
}
public void setRunning(boolean run) {
_run = run;
}
public SurfaceHolder getSurfaceHolder() {
return _surfaceHolder;
}
@Override
public void run() {
Canvas c;
while (_run) {
c = null;
try {
c = _surfaceHolder.lockCanvas(null);
synchronized (_surfaceHolder) {
_panel.onDraw(c);
}
} finally {
// do this in a finally so that if an exception is thrown
// during the above, we don't leave the Surface in an
// inconsistent state
if (c != null) {
_surfaceHolder.unlockCanvasAndPost(c);
}
}
}
}
}//end of PanelThread
}//end of Panel
我遇到的问题是，一旦我初次调用Panel类，我将从服务中获取新记录，因此，我的Info Map数据结构将会更新。但是，我的Panel类只是陷入循环，从不接收任何新的Data对象。我发现的SurfaceViews的所有示例都涉及在SurfaceView类本身内更新它们的方法（例如触摸屏幕并创建新图像等）。遗憾的是，我对这个特定问题感到困惑。有没有更好的方法来设计我的Activity / SurfaceView交互？是否需要额外的视图？
答案 0 :(得分：1)
通过快速查看代码，我认为问题是您正在尝试从UI线程更新数据结构，同时在PanelThread中对其进行操作。它看起来你的Activity类和Panel也不同步 - 我没有在Panel类中看到setData方法，但我认为它更新了测试静态成员变量。
我的建议：
1 - 测试不应该是静态的 - 它基本上与该类的实例相关联。 2 - 触摸数据时使用同步（测试）。这应该用于设置和读取数据。 3 - 在运行循环中进行睡眠或等待调用 - 这为活动UI线程提供了更新测试的时间。还节省了电池，并允许您选择帧速率进行更新。