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我的應用程序表現爲隨機退出。當我在API級別10上運行它時，它工作得很好。但是，當我在API級別14運行它，它顯示下列情況除外：無法在Android 4.0上啓動活動ComponentInfo
12-26 12:19:18.021: W/dalvikvm(1594): threadid=1: thread exiting with uncaught exception (group=0xb5f18288)
12-26 12:19:18.051: E/AndroidRuntime(1594): FATAL EXCEPTION: main
12-26 12:19:18.051: E/AndroidRuntime(1594): java.lang.RuntimeException: Unable to start activity ComponentInfo{tariq.buynow3/tariq.buynow3.CameraTestActivity}: java.lang.NullPointerException
12-26 12:19:18.051: E/AndroidRuntime(1594): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2059)
12-26 12:19:18.051: E/AndroidRuntime(1594): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2084)
12-26 12:19:18.051: E/AndroidRuntime(1594): at android.app.ActivityThread.access$600(ActivityThread.java:130)
12-26 12:19:18.051: E/AndroidRuntime(1594): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1195)
12-26 12:19:18.051: E/AndroidRuntime(1594): at android.os.Handler.dispatchMessage(Handler.java:99)
12-26 12:19:18.051: E/AndroidRuntime(1594): at android.os.Looper.loop(Looper.java:137)
12-26 12:19:18.051: E/AndroidRuntime(1594): at android.app.ActivityThread.main(ActivityThread.java:4745)
12-26 12:19:18.051: E/AndroidRuntime(1594): at java.lang.reflect.Method.invokeNative(Native Method)
12-26 12:19:18.051: E/AndroidRuntime(1594): at java.lang.reflect.Method.invoke(Method.java:511)
12-26 12:19:18.051: E/AndroidRuntime(1594): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:786)
12-26 12:19:18.051: E/AndroidRuntime(1594): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
12-26 12:19:18.051: E/AndroidRuntime(1594): at dalvik.system.NativeStart.main(Native Method)
12-26 12:19:18.051: E/AndroidRuntime(1594): Caused by: java.lang.NullPointerException
12-26 12:19:18.051: E/AndroidRuntime(1594): at tariq.buynow3.CameraTestActivity.onCreate(CameraTestActivity.java:76)
12-26 12:19:18.051: E/AndroidRuntime(1594): at android.app.Activity.performCreate(Activity.java:5008)
12-26 12:19:18.051: E/AndroidRuntime(1594): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1079)
12-26 12:19:18.051: E/AndroidRuntime(1594): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2023)
12-26 12:19:18.051: E/AndroidRuntime(1594): ... 11 more
CameraTestActivity如下
/*
* Basic no frills app which integrates the ZBar barcode scanner with
* the camera.
*
* Created by lisah0 on 2012-02-24
*/
package tariq.buynow3;
import net.sourceforge.zbar.Config;
import net.sourceforge.zbar.Image;
import net.sourceforge.zbar.ImageScanner;
import net.sourceforge.zbar.Symbol;
import net.sourceforge.zbar.SymbolSet;
import android.app.Activity;
import android.content.Intent;
import android.content.pm.ActivityInfo;
import android.hardware.Camera;
import android.hardware.Camera.AutoFocusCallback;
import android.hardware.Camera.PreviewCallback;
import android.hardware.Camera.Size;
import android.os.Bundle;
import android.os.Handler;
import android.view.View;
import android.widget.Button;
import android.widget.FrameLayout;
import android.widget.TextView;
/* Import ZBar Class files */
public class CameraTestActivity extends Activity
{
private Camera mCamera;
private CameraPreview mPreview;
private Handler autoFocusHandler;
TextView scanText;
Button scanButton;
ImageScanner scanner;
@SuppressWarnings("unused")
private boolean barcodeScanned = false;
private boolean previewing = true;
static {
System.loadLibrary("iconv");
}
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_PORTRAIT);
autoFocusHandler = new Handler();
mCamera = getCameraInstance();
/* Instance barcode scanner */
scanner = new ImageScanner();
scanner.setConfig(0, Config.X_DENSITY, 3);
scanner.setConfig(0, Config.Y_DENSITY, 3);
FrameLayout preview = (FrameLayout)findViewById(R.id.cameraPreview);
mPreview = new CameraPreview(this, mCamera, previewCb, autoFocusCB);
preview.addView(mPreview);
scanText = (TextView)findViewById(R.id.scanText);
Intent in = new Intent();
setResult(-1,in);
/*scanButton = (Button)findViewById(R.id.ScanButton);
/* scanButton.setOnClickListener(new OnClickListener() {
public void onClick(View v) {
if (barcodeScanned) {
barcodeScanned = false;
scanText.setText("Scanning...");*/
mCamera.setPreviewCallback(previewCb);
mCamera.startPreview();
previewing = true;
mCamera.autoFocus(autoFocusCB);/*
}
}
});*/
}
public void onPause() {
super.onPause();
releaseCamera();
}
/** A safe way to get an instance of the Camera object. */
public static Camera getCameraInstance(){
Camera c = null;
try {
c = Camera.open();
} catch (Exception e){
}
return c;
}
private void releaseCamera() {
if (mCamera != null) {
previewing = false;
mCamera.setPreviewCallback(null);
mCamera.release();
mCamera = null;
}
}
private Runnable doAutoFocus = new Runnable() {
public void run() {
if (previewing)
mCamera.autoFocus(autoFocusCB);
}
};
PreviewCallback previewCb = new PreviewCallback() {
public void onPreviewFrame(byte[] data, Camera camera) {
Camera.Parameters parameters = camera.getParameters();
Size size = parameters.getPreviewSize();
Image barcode = new Image(size.width, size.height, "Y800");
barcode.setData(data);
int result = scanner.scanImage(barcode);
if (result != 0) {
previewing = false;
mCamera.setPreviewCallback(null);
mCamera.stopPreview();
SymbolSet syms = scanner.getResults();
String resultStr="";
for (Symbol sym : syms) {
resultStr += sym.getData();
barcodeScanned = true;
}
scanText.setText("Done");
Intent intent=new Intent();
intent.putExtra("Text",resultStr);
setResult(1, intent);
finish();
}
}
};
// Mimic continuous auto-focusing
AutoFocusCallback autoFocusCB = new AutoFocusCallback() {
public void onAutoFocus(boolean success, Camera camera) {
autoFocusHandler.postDelayed(doAutoFocus, 1000);
}
};
public void CancelScan(View view){
barcodeScanned = false;
/*Intent in = new Intent();
setResult(-1,in);*/
finish();
}
}
佈局本次活動是：
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical"
android:layout_width="match_parent"
android:layout_height="match_parent">
<FrameLayout
android:id="@+id/cameraPreview"
android:layout_width="match_parent"
android:layout_height="0dp"
android:layout_weight="1"
/>
<TextView
android:id="@+id/scanText"
android:layout_width="106dp"
android:layout_height="wrap_content"
android:text="@string/scanning" />
<Button
android:id="@+id/button1"
style="?android:attr/buttonStyleSmall"
android:layout_width="144dp"
android:layout_height="wrap_content"
android:layout_gravity="center"
android:text="@string/Cancel"
android:onClick="CancelScan" />
</LinearLayout>
和明顯我的應用程序如下：
<uses-sdk
android:minSdkVersion="8"
android:targetSdkVersion="17" />
<uses-permission android:name="android.permission.CAMERA" />
<uses-feature android:name="android.hardware.camera" />
<uses-feature android:name="android.hardware.camera.autofocus" />
<application
android:allowBackup="true"
android:icon="@drawable/ic_launcher"
android:label="@string/app_name"
android:theme="@style/AppTheme" >
<activity
android:name="tariq.buynow3.MainActivity"
android:label="@string/app_name" >
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
<activity
android:name="tariq.buynow3.CameraTestActivity"
android:label="@string/app_name" >
<intent-filter>
<action android:name="android.intent.action.MAIN"/>
<category android:name="android.intent.category.DEFAULT"/>
</intent-filter>
</activity>
<activity
android:name="tariq.buynow3.BuyingActivity"
android:label="@string/title_activity_buying" >
</activity>
</application>
</manifest>
這與this有什麼關係？
什麼開始CameraTestActivity？ MainActivity？ – smichak
嘗試調試您的相機活動代碼並在方法onCreate（） 上應用中斷點你在這裏得到空指針異常 –
那麼第76行是什麼？ – Egor