我正在开发不同的类并从这些类中定义对象 对于每个对象，当按下按钮或触摸屏幕时，我正在调用一些函数
我想将对象放在this link
中的图片中当我使用以下方式放置这些对象时，我无法调用每个类的函数
这是我正在使用的代码，我是从Android and MJPEG
获取的主要活动
package de.mjpegsample;
import android.app.Activity;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;
import android.view.Window;
import android.view.WindowManager;
import de.mjpegsample.MjpegView.MjpegInputStream;
import de.mjpegsample.MjpegView.MjpegView;
public class MjpegSample extends Activity {
private MjpegView mv;
private MjpegView mv2;
private static final int MENU_QUIT = 1;
public void onCreate(Bundle icicle) {
super.onCreate(icicle);
setContentView(R.layout.activity_main);
//sample public cam
String URL = "http://gamic.dnsalias.net:7001/img/video.mjpeg";
mv = (MjpegView)findViewById(R.id.mjpegView1);
mv2 = (MjpegView)findViewById(R.id.mjpegView2);
}
@Override
protected void onResume() {
super.onResume();
mv.init(this);
mv2.init(this);
}
public void onPause() {
super.onPause();
mv.stopPlayback();
}
}
MjpegView类
package de.mjpegsample.MjpegView;
import java.io.IOException;
import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.graphics.PorterDuff;
import android.graphics.PorterDuffXfermode;
import android.graphics.Rect;
import android.graphics.Typeface;
import android.util.AttributeSet;
import android.view.SurfaceHolder;
import android.view.SurfaceView;
public class MjpegView extends SurfaceView implements SurfaceHolder.Callback {
public final static int POSITION_UPPER_LEFT = 9;
public final static int POSITION_UPPER_RIGHT = 3;
public final static int POSITION_LOWER_LEFT = 12;
public final static int POSITION_LOWER_RIGHT = 6;
public final static int SIZE_STANDARD = 1;
public final static int SIZE_BEST_FIT = 4;
public final static int SIZE_FULLSCREEN = 8;
private MjpegViewThread thread;
private MjpegInputStream mIn = null;
private boolean showFps = false;
private boolean mRun = false;
private boolean surfaceDone = false;
private Paint overlayPaint;
private int overlayTextColor;
private int overlayBackgroundColor;
private int ovlPos;
private int dispWidth;
private int dispHeight;
private int displayMode;
public class MjpegViewThread extends Thread {
private SurfaceHolder mSurfaceHolder;
private int frameCounter = 0;
private long start;
private Bitmap ovl;
public MjpegViewThread(SurfaceHolder surfaceHolder, Context context) { mSurfaceHolder = surfaceHolder; }
private Rect destRect(int bmw, int bmh) {
int tempx;
int tempy;
if (displayMode == MjpegView.SIZE_STANDARD) {
tempx = (dispWidth / 2) - (bmw / 2);
tempy = (dispHeight / 2) - (bmh / 2);
return new Rect(tempx, tempy, bmw + tempx, bmh + tempy);
}
if (displayMode == MjpegView.SIZE_BEST_FIT) {
float bmasp = (float) bmw / (float) bmh;
bmw = dispWidth;
bmh = (int) (dispWidth / bmasp);
if (bmh > dispHeight) {
bmh = dispHeight;
bmw = (int) (dispHeight * bmasp);
}
tempx = (dispWidth / 2) - (bmw / 2);
tempy = (dispHeight / 2) - (bmh / 2);
return new Rect(tempx, tempy, bmw + tempx, bmh + tempy);
}
if (displayMode == MjpegView.SIZE_FULLSCREEN) return new Rect(0, 0, dispWidth, dispHeight);
return null;
}
public void setSurfaceSize(int width, int height) {
synchronized(mSurfaceHolder) {
dispWidth = width;
dispHeight = height;
}
}
private Bitmap makeFpsOverlay(Paint p, String text) {
Rect b = new Rect();
p.getTextBounds(text, 0, text.length(), b);
int bwidth = b.width()+2;
int bheight = b.height()+2;
Bitmap bm = Bitmap.createBitmap(bwidth, bheight, Bitmap.Config.ARGB_8888);
Canvas c = new Canvas(bm);
p.setColor(overlayBackgroundColor);
c.drawRect(0, 0, bwidth, bheight, p);
p.setColor(overlayTextColor);
c.drawText(text, -b.left+1, (bheight/2)-((p.ascent()+p.descent())/2)+1, p);
return bm;
}
public void run() {
start = System.currentTimeMillis();
PorterDuffXfermode mode = new PorterDuffXfermode(PorterDuff.Mode.DST_OVER);
Bitmap bm;
int width;
int height;
Rect destRect;
Canvas c = null;
Paint p = new Paint();
String fps = "";
while (mRun) {
if(surfaceDone) {
try {
c = mSurfaceHolder.lockCanvas();
synchronized (mSurfaceHolder) {
try {
bm = mIn.readMjpegFrame();
destRect = destRect(bm.getWidth(),bm.getHeight());
c.drawColor(Color.BLACK);
c.drawBitmap(bm, null, destRect, p);
if(showFps) {
p.setXfermode(mode);
if(ovl != null) {
height = ((ovlPos & 1) == 1) ? destRect.top : destRect.bottom-ovl.getHeight();
width = ((ovlPos & 8) == 8) ? destRect.left : destRect.right -ovl.getWidth();
c.drawBitmap(ovl, width, height, null);
}
p.setXfermode(null);
frameCounter++;
if((System.currentTimeMillis() - start) >= 1000) {
fps = String.valueOf(frameCounter)+"fps";
frameCounter = 0;
start = System.currentTimeMillis();
ovl = makeFpsOverlay(overlayPaint, fps);
}
}
} catch (IOException e) {}
}
} finally { if (c != null) mSurfaceHolder.unlockCanvasAndPost(c); }
}
}
}
}
private void init(Context context) {
SurfaceHolder holder = getHolder();
holder.addCallback(this);
thread = new MjpegViewThread(holder, context);
setFocusable(true);
overlayPaint = new Paint();
overlayPaint.setTextAlign(Paint.Align.LEFT);
overlayPaint.setTextSize(12);
overlayPaint.setTypeface(Typeface.DEFAULT);
overlayTextColor = Color.WHITE;
overlayBackgroundColor = Color.BLACK;
ovlPos = MjpegView.POSITION_LOWER_RIGHT;
displayMode = MjpegView.SIZE_STANDARD;
dispWidth = getWidth();
dispHeight = getHeight();
}
public void startPlayback() {
if(mIn != null) {
mRun = true;
thread.start();
}
}
public void stopPlayback() {
mRun = false;
boolean retry = true;
while(retry) {
try {
thread.join();
retry = false;
} catch (InterruptedException e) {}
}
}
public MjpegView(Context context, AttributeSet attrs) { super(context, attrs); init(context); }
public void surfaceChanged(SurfaceHolder holder, int f, int w, int h) { thread.setSurfaceSize(w, h); }
public void surfaceDestroyed(SurfaceHolder holder) {
surfaceDone = false;
stopPlayback();
}
public MjpegView(Context context) {
super(context);
init(context);
}
public void surfaceCreated(SurfaceHolder holder) {
surfaceDone = true;
}
public void showFps(boolean b) {
showFps = b;
}
public void setSource(MjpegInputStream source) {
mIn = source;
startPlayback();
}
public void setOverlayPaint(Paint p) {
overlayPaint = p;
}
public void setOverlayTextColor(int c) {
overlayTextColor = c;
}
public void setOverlayBackgroundColor(int c) {
overlayBackgroundColor = c;
}
public void setOverlayPosition(int p) {
ovlPos = p;
}
public void setDisplayMode(int s) {
displayMode = s;
}
}
MjpegInputStream类
package de.mjpegsample.MjpegView;
import java.io.BufferedInputStream;
import java.io.ByteArrayInputStream;
import java.io.DataInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.net.URI;
import java.util.Properties;
import org.apache.http.HttpResponse;
import org.apache.http.client.ClientProtocolException;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.impl.client.DefaultHttpClient;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
public class MjpegInputStream extends DataInputStream {
private final byte[] SOI_MARKER = { (byte) 0xFF, (byte) 0xD8 };
private final byte[] EOF_MARKER = { (byte) 0xFF, (byte) 0xD9 };
private final String CONTENT_LENGTH = "Content-Length";
private final static int HEADER_MAX_LENGTH = 100;
private final static int FRAME_MAX_LENGTH = 40000 + HEADER_MAX_LENGTH;
private int mContentLength = -1;
public static MjpegInputStream read(String url) {
HttpResponse res;
DefaultHttpClient httpclient = new DefaultHttpClient();
try {
res = httpclient.execute(new HttpGet(URI.create(url)));
return new MjpegInputStream(res.getEntity().getContent());
} catch (ClientProtocolException e) {
} catch (IOException e) {}
return null;
}
public MjpegInputStream(InputStream in) { super(new BufferedInputStream(in, FRAME_MAX_LENGTH)); }
private int getEndOfSeqeunce(DataInputStream in, byte[] sequence) throws IOException {
int seqIndex = 0;
byte c;
for(int i=0; i < FRAME_MAX_LENGTH; i++) {
c = (byte) in.readUnsignedByte();
if(c == sequence[seqIndex]) {
seqIndex++;
if(seqIndex == sequence.length) return i + 1;
} else seqIndex = 0;
}
return -1;
}
private int getStartOfSequence(DataInputStream in, byte[] sequence) throws IOException {
int end = getEndOfSeqeunce(in, sequence);
return (end < 0) ? (-1) : (end - sequence.length);
}
private int parseContentLength(byte[] headerBytes) throws IOException, NumberFormatException {
ByteArrayInputStream headerIn = new ByteArrayInputStream(headerBytes);
Properties props = new Properties();
props.load(headerIn);
return Integer.parseInt(props.getProperty(CONTENT_LENGTH));
}
public Bitmap readMjpegFrame() throws IOException {
mark(FRAME_MAX_LENGTH);
int headerLen = getStartOfSequence(this, SOI_MARKER);
reset();
byte[] header = new byte[headerLen];
readFully(header);
try {
mContentLength = parseContentLength(header);
} catch (NumberFormatException nfe) {
mContentLength = getEndOfSeqeunce(this, EOF_MARKER);
}
reset();
byte[] frameData = new byte[mContentLength];
skipBytes(headerLen);
readFully(frameData);
return BitmapFactory.decodeStream(new ByteArrayInputStream(frameData));
}
}
所以我现在要做的就是添加两个对象，这样我就可以得到两个正方形的流媒体 如果用户单击，我想添加一个按钮，然后显示流路径的信息
这是我的xlm文件
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical" >
<LinearLayout
android:id="@+id/r1"
android:layout_width="fill_parent"
android:layout_height="0dp"
android:layout_weight="1"
android:orientation="horizontal" >
<Button
android:id="@+id/button1"
android:layout_width="0dp"
android:layout_height="match_parent"
android:layout_weight="1"
android:text="Button" />
<de.mjpegsample.MjpegView
android:id="@+id/mjpegView1"
android:layout_width="0dp"
android:layout_height="match_parent"
android:layout_weight="1" >
</LinearLayout>
<LinearLayout
android:id="@+id/r2"
android:layout_width="fill_parent"
android:layout_height="0dp"
android:layout_weight="1" >
<de.mjpegsample.MjpegView
android:id="@+id/mjpegView2"
android:layout_width="0dp"
android:layout_height="match_parent"
android:layout_weight="1" >
</LinearLayout>
</LinearLayout>
另一件事是想要添加一些当用户触摸流媒体屏幕时会执行的功能，但我仍然想知道如何才能这样做
现在我的问题是有另一种方法将我的对象放在我的布局上而不是我正在使用的方式，我的意思是我可以将我的对象定义为
MyClass obj1 = new MyClass(this);这样我可以毫无问题地调用函数
或者是否有其他方法可以解决此问题
这是来自logcat的错误消息
11-20 11:06:32.732: E/AndroidRuntime(5620): FATAL EXCEPTION: main
11-20 11:06:32.732: E/AndroidRuntime(5620): java.lang.RuntimeException: Unable to resume activity {com.example.firstapp/com.example.firstapp.MainActivity}: java.lang.NullPointerException
11-20 11:06:32.732: E/AndroidRuntime(5620): at android.app.ActivityThread.performResumeActivity(ActivityThread.java:2790)
11-20 11:06:32.732: E/AndroidRuntime(5620): at android.app.ActivityThread.handleResumeActivity(ActivityThread.java:2819)
11-20 11:06:32.732: E/AndroidRuntime(5620): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2266)
11-20 11:06:32.732: E/AndroidRuntime(5620): at android.app.ActivityThread.access$600(ActivityThread.java:141)
11-20 11:06:32.732: E/AndroidRuntime(5620): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1256)
11-20 11:06:32.732: E/AndroidRuntime(5620): at android.os.Handler.dispatchMessage(Handler.java:99)
11-20 11:06:32.732: E/AndroidRuntime(5620): at android.os.Looper.loop(Looper.java:137)
11-20 11:06:32.732: E/AndroidRuntime(5620): at android.app.ActivityThread.main(ActivityThread.java:5103)
11-20 11:06:32.732: E/AndroidRuntime(5620): at java.lang.reflect.Method.invokeNative(Native Method)
11-20 11:06:32.732: E/AndroidRuntime(5620): at java.lang.reflect.Method.invoke(Method.java:525)
11-20 11:06:32.732: E/AndroidRuntime(5620): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:737)
11-20 11:06:32.732: E/AndroidRuntime(5620): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
11-20 11:06:32.732: E/AndroidRuntime(5620): at dalvik.system.NativeStart.main(Native Method)
11-20 11:06:32.732: E/AndroidRuntime(5620): Caused by: java.lang.NullPointerException
11-20 11:06:32.732: E/AndroidRuntime(5620): at com.example.firstapp.MainActivity.onResume(MainActivity.java:137)
11-20 11:06:32.732: E/AndroidRuntime(5620): at android.app.Instrumentation.callActivityOnResume(Instrumentation.java:1192)
11-20 11:06:32.732: E/AndroidRuntime(5620): at android.app.Activity.performResume(Activity.java:5211)
11-20 11:06:32.732: E/AndroidRuntime(5620): at android.app.ActivityThread.performResumeActivity(ActivityThread.java:2780)
11-20 11:06:32.732: E/AndroidRuntime(5620): ... 12 more
我尝试这样做只是为了测试它是否会起作用并且同样的事情发生了应用程序崩溃
FrameLayout f1;
f1 = (FrameLayout)findViewById(R.id.frame1);
TextView t = new TextView(getApplicationContext());
t.setText("Hello world");
f1.addView(t);
但是当我尝试这个时它起作用了
FrameLayout f1 = new FrameLayout(this);
TextView t = new TextView(getApplicationContext());
t.setText("Hello world");
f1.addView(t);