Android开发ImageView图片无法显示解决过程

public class ActiEnvi extends Activity {
static final String TAG = "ActiEnvi";
private static final int REQ_CODE_CAMERA = 0x1;

private String imgpath = "";
private String tempath = "";
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.acti_envi);

......
}
......
@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
// 拍照成功并返回
if (requestCode == REQ_CODE_CAMERA
&& resultCode == Activity.RESULT_OK) {
this.imgpath = tempath;
Bitmap bm = BitmapFactory.decodeFile(this.imgpath);
imgView.setImageBitmap(bm);
imgView.setScaleType(ScaleType.FIT_CENTER);
}
}

.......
// 调用系统相机拍照
protected void captureImage() {
Intent intent = new Intent(MediaStore.ACTION_IMAGE_CAPTURE);
tempath = IOHelper.generateImgPath();
File out = new File(tempath);
intent.putExtra(MediaStore.EXTRA_OUTPUT, Uri.fromFile(out));
startActivityForResult(intent, REQ_CODE_CAMERA);
}
......
}

<uses-sdk android:minSdkVersion="8" />
<!-- android:targetSdkVersion="17" -->