安卓：startActivityForResult总是空，并强制关闭我的应用程序 [英] Android: startActivityForResult always null and force close my app
问题描述
我有以下情形颇为拉我的头发了：我正在写一个类来管理Android摄像头，它扩展了活动。在那个班我下面的code。什么情况是，我总是得到零点异常--with其强制关闭小friend--在该行，上面写着：
startActivityForResult（意向，0）;
不过，我得到的System.out.println（故意不为空）;在LogCat中...
印确定在LogCat中说：
03-08 22：46：38.584：ERROR / AndroidRuntime（1079）：显示java.lang.NullPointerException
03-08 22：46：38.584：ERROR / AndroidRuntime（1079）：在android.app.Activity.startActivityForResult（Activity.java:2749）
03-08 22：46：38.584：ERROR / AndroidRuntime（1079）：在com.test.cameratest.startCameraActivity（cameratest.java:39）
在清单中，我有：
＆LT;使用-权限的Android：名称=android.permission.WRITE_EXTERNAL_STORAGE/＆GT;
＆LT;使用-权限的Android：名称=android.permission.CAMERA/＆GT;
＆LT;使用特征的android：NAME =android.hardware.camera/＆GT;
＆LT;活动机器人：cameratestNAME = /＆GT;
所以，我在做什么错了？为什么startActivityForResult总是抛出空！？
@覆盖
公共无效的onCreate（包savedInstanceState）
{
super.onCreate（savedInstanceState）;
}
/ **根据建议，试图改变方法，从受保护的私人或公共
但仍然有同样的问题* /
保护无效startCameraActivity（）
{
字符串路径=（新StringBuilder()).append(Environment.getExternalStorageDirectory()).append("/images/test.jpg").toString();
的System.out.println（开始）;
档案文件=新的文件（路径）;
的System.out.println（路径）;
乌里outputFileUri = Uri.fromFile（文件）;
意向意图=新的意图（android.media.action.IMAGE_CAPTURE）;
intent.putExtra（输出，outputFileUri）;
/ **删除按照建议
如果（意向！= NULL）
{
的System.out.println（故意不为空）;
** startActivityForResult（意向，0）; **
}
* /
** startActivityForResult（意向，0）; **＆LT; ==空指针异常
}
编辑：
根据建议，我接过来一看行2749对Activity.java从Android的2.1r2框架，这里是code：
公共无效startActivityForResult（意向意图，诠释请求code）{
如果（mParent == NULL）{
****线2749是如下因素
Instrumentation.ActivityResult AR =
mInstrumentation.execStartActivity（
对此，mMainThread.getApplicationThread（），mToken，这一点，
意图，请求code）;
****
如果（AR！= NULL）{
mMainThread.sendActivityResult（
mToken，mEmbeddedID，请求code，ar.getResult code（）
ar.getResultData（））;
}
如果（要求code取代; = 0）{
//如果这个开始请求的结果，我们能够避免
//活性可见，直到结果被接收。环境
//的onCreate（捆绑savedInstanceState）或onResume（在此code）将保持
//活动在这段时间隐藏的，以避免闪烁。
//当结果被请求，因为这只能进行
//，保证我们获取信息回来的时候
//活动完成后，不管发生了什么。
mStartedActivity =真;
}
} 其他 {
mParent.startActivityFromChild（这一点，意图，请求code）;
}
}
线2749标有双**不过，我看不出与code问题
EDITED
忘了解释我是怎么称呼这样的：
cameratest凸轮=新cameratest（）;
cam.startCameraActivity（）;
下面的文章提供了一个解决此问题的，不仅为三星设备（我对HTC Desire Z的一个相同的问题，运行Android的改装2.3.7）：
<一个href="http://kevinpotgieter.word$p$pss.com/2011/03/30/null-intent-passed-back-on-samsung-galaxy-tab/" rel="nofollow">http://kevinpotgieter.word$p$pss.com/2011/03/30/null-intent-passed-back-on-samsung-galaxy-tab/
我知道这是很尴尬的，但它的作品。总之，它表明放弃尝试获取原意，只是告诉您如何获取句柄拍摄的照片。
I have the following scenario which is quite pulling my hairs out: I'm writing a class to manage the Android camera, which extends Activity. Inside that class I have the code below. What happens is that I always get null point exception --with its force close little friend-- in the line that says:
startActivityForResult(intent, 0);
However I get System.out.println("intent not null"); printed ok in LogCat...
The LogCat says:
03-08 22:46:38.584: ERROR/AndroidRuntime(1079): java.lang.NullPointerException
03-08 22:46:38.584: ERROR/AndroidRuntime(1079): at android.app.Activity.startActivityForResult(Activity.java:2749)
03-08 22:46:38.584: ERROR/AndroidRuntime(1079): at com.test.cameratest.startCameraActivity(cameratest.java:39)
In the manifest I have:
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
<uses-permission android:name="android.permission.CAMERA" />
<uses-feature android:name="android.hardware.camera"/>
<activity android:name=".cameratest" />
So, what I'm doing wrong?? Why startActivityForResult always throws null!?
@Override
public void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
}
/** As per suggestion tried to change the method from protected to private or public
but still have the same problem */
protected void startCameraActivity()
{
String path = (new StringBuilder()).append(Environment.getExternalStorageDirectory()).append("/images/test.jpg").toString();
System.out.println("started");
File file = new File(path);
System.out.println(path);
Uri outputFileUri = Uri.fromFile(file);
Intent intent = new Intent("android.media.action.IMAGE_CAPTURE");
intent.putExtra("output", outputFileUri);
/** Removed as per suggestion
if (intent!=null)
{
System.out.println("intent not null");
**startActivityForResult(intent, 0);**
}
*/
**startActivityForResult(intent, 0);** <== null pointer exception
}
EDITED:
As per suggestion, I took a look to line 2749 on Activity.java from Android 2.1r2 framework and here is the code:
public void startActivityForResult(Intent intent, int requestCode) {
if (mParent == null) {
**** Line 2749 is the folowing
Instrumentation.ActivityResult ar =
mInstrumentation.execStartActivity(
this, mMainThread.getApplicationThread(), mToken, this,
intent, requestCode);
****
if (ar != null) {
mMainThread.sendActivityResult(
mToken, mEmbeddedID, requestCode, ar.getResultCode(),
ar.getResultData());
}
if (requestCode >= 0) {
// If this start is requesting a result, we can avoid making
// the activity visible until the result is received. Setting
// this code during onCreate(Bundle savedInstanceState) or onResume() will keep the
// activity hidden during this time, to avoid flickering.
// This can only be done when a result is requested because
// that guarantees we will get information back when the
// activity is finished, no matter what happens to it.
mStartedActivity = true;
}
} else {
mParent.startActivityFromChild(this, intent, requestCode);
}
}
Line 2749 is marked with double ** However, I don't see a problem with that code
EDITED
Forgot to explain how I call this:
cameratest cam = new cameratest();
cam.startCameraActivity();
The following article provides a workaround to this problem, not only for Samsung devices (I have an identical issue on HTC Desire Z running modded Android 2.3.7):
http://kevinpotgieter.wordpress.com/2011/03/30/null-intent-passed-back-on-samsung-galaxy-tab/
I realize it is quite awkward, but it works. To summarize, it suggests giving up attempts to get the original intent and just tells how to obtain a handle the captured photo.
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