【发布时间】：2017-04-20 20:08:51
【问题描述】：
我遇到了有关 getSystemService 方法的问题，因为 Android Studio IDE 一直告诉我它无法解决此方法。据我所知，这可能来自于我的班级不包含活动的事实。我正在阅读有关 getSystemService 问题的相关主题，但我根本找不到任何匹配的解决方案。
我把我的代码放在上面
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.Canvas;
import android.graphics.Matrix;
import android.graphics.Rect;
import android.hardware.Camera;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.TextView;
public class MainActivity extends AppCompatActivity {
private Camera mCamera;
private CameraView mCameraView;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
}
@Override
protected void onResume(){
super.onResume();
try{
mCamera = Camera.open(1);
mCameraView = new CameraView(this, mCamera);
setContentView(mCameraView);
} catch (Exception e){
finish();
}
}
@Override
protected void onPause(){
if(mCamera != null){
mCamera.release();
mCamera = null;
}
super.onPause();
}
}
上面的粗体字是我想弄清楚的那个
import android.content.Context;
import android.hardware.Camera;
import android.hardware.Camera.Parameters;
import android.util.Log;
import android.view.SurfaceHolder;
import android.view.SurfaceView;
import android.view.View;
import android.view.Surface;
import android.view.Display;
import android.view.WindowManager;
import java.io.IOException;
import android.app.Activity;
import java.util.List;
public class CameraView extends SurfaceView implements SurfaceHolder.Callback{
private Camera mCamera;
private View mView;
private WindowManager display;
public CameraView(Context context, Camera mCamera) {
super(context);
this.mCamera = mCamera;
mCamera.setDisplayOrientation(90);
SurfaceHolder holder = getHolder();
holder.addCallback(this);
holder.setType(SurfaceHolder.SURFACE_TYPE_PUSH_BUFFERS);
}
@Override
public void surfaceCreated(SurfaceHolder holder) {
try{
mCamera.setPreviewDisplay(holder);
mCamera.startPreview();
} catch (IOException e) {
Log.e("cameraPreview", "The failure of the camera settings");
}
}
@Override
public void surfaceChanged(SurfaceHolder holder, int format, int width, int height) {
Camera.Parameters params = mCamera.getParameters();
List<Camera.Size> sizes = params.getSupportedPreviewSizes();
Camera.Size optionalSize = getOptimalPreviewSize(sizes, width, height);
params.setPreviewSize(optionalSize.width, optionalSize.height);
mCamera.setParameters(params);
boolean isPreviewRunning = true;
if (isPreviewRunning)
{
mCamera.stopPreview();
}
Parameters parameters = mCamera.getParameters();
Display display = ((WindowManager) getSystemService(Context.WINDOW_SERVICE)).getDefaultDisplay();
if(display.getRotation() == Surface.ROTATION_0)
{
parameters.setPreviewSize(height, width);
mCamera.setDisplayOrientation(90);
}
if(display.getRotation() == Surface.ROTATION_90)
{
parameters.setPreviewSize(width, height);
}
if(display.getRotation() == Surface.ROTATION_180)
{
parameters.setPreviewSize(height, width);
}
if(display.getRotation() == Surface.ROTATION_270)
{
parameters.setPreviewSize(width, height);
mCamera.setDisplayOrientation(180);
}
mCamera.setParameters(parameters);
previewCamera();
}
public void previewCamera()
{
try
{
mCamera.setPreviewDisplay();
mCamera.startPreview();
boolean isPreviewRunning = true;
}
catch(Exception e)
{
Log.d(APP_CLASS, "Cannot start preview", e);
}
}
@Override
public void surfaceDestroyed(SurfaceHolder holder) {
mCamera.release();
mCamera = null;
}
private Camera.Size getOptimalPreviewSize(List<Camera.Size> sizes, int w, int h) {
final double ASPECT_TOLERANCE = 0.1;
double targetRatio=(double)h / w;
if (sizes == null) return null;
Camera.Size optimalSize = null;
double minDiff = Double.MAX_VALUE;
int targetHeight = h;
for (Camera.Size size : sizes) {
double ratio = (double) size.width / size.height;
if (Math.abs(ratio - targetRatio) > ASPECT_TOLERANCE) continue;
if (Math.abs(size.height - targetHeight) < minDiff) {
optimalSize = size;
minDiff = Math.abs(size.height - targetHeight);
}
}
if (optimalSize == null) {
minDiff = Double.MAX_VALUE;
for (Camera.Size size : sizes) {
if (Math.abs(size.height - targetHeight) < minDiff) {
optimalSize = size;
minDiff = Math.abs(size.height - targetHeight);
}
}
}
return optimalSize;
}
}
你能告诉我应该怎么做才能避免这件事吗？
谢谢！
【问题讨论】：
标签： java android android-studio methods resolve