android - 无法解决方法getSystemService问题

时间：2016-12-06 08:40:45

标签： java android android-studio methods resolve

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，可能是因为我的班级不包含活动。我正在阅读有关getSystemService问题的相关主题，但我根本无法找到任何匹配的解决方案。

我将代码放在上面

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();


   }

}

上面那个大胆的一个是我试图找出的那个

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;


  }



}

你能否告诉我如何避免这件事呢？

谢谢！

4 个答案:

答案 0 :(得分：13)

您需要在getSystemService上致电Context，因此，为什么它在您的CameraView中无效。您可以将已传入的上下文存储为字段，并在其上调用getSystemService。请参阅以下修改后的代码：

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;
private Context mContext;


public CameraView(Context context, Camera mCamera) {
    super(context);

    mContext = 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) mContext.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;


  }

答案 1 :(得分：2)

您应该使用getActivity()来解决此问题：

getActivity().getSystemService(Context.AUDIO_SERVICE);

这对我有用

答案 2 :(得分：2)

有时这是由于android studio无法获取特定文件而导致，可以通过清理和重建项目来解决。 如果清洁和重建没有效果。 像这样使用getSystemService。

这对我有用：

#include<linux/list.h>
#include<linux/init.h>
#include<linux/kernel.h>
#include<linux/module.h>
#include<linux/types.h>
#include<linux/slab.h>

struct birthday {
    int day;
    int month;
    int year;
    struct list_head list;
}

static LIST_HEAD(birthday_list);
static void remove_oldest_student(void){
struct birthday *max, *curr, *next;
//point max to list head
max = LIST_HEAD(birthday_list);

list_for_each_entry(curr, &birthday_list, list){

  //find_max(&max, &curr);
}

    printk(KERN_INFO "Oldest Student Details --> Name: %s, Month: %d, Day: %d, Year: %d\n",max->name, max->month,max->day,max->year);
}


int simple_init(void) {
    struct birthday *ptr;
    int i;
    for(i = 0; i < 5; i++) {
        // create 5 birthday structs and add them to the list

        struct birthday *person;
        person = kmalloc(sizeof(*person), GFP_KERNEL);
        person->day = 22;
        person->month = 11;
        person->year = 1981;
        INIT_LIST_HEAD(&person->list);

        list_add_tail(&person->list, &birthday_list);
    }

    list_for_each_entry(ptr, &birthday_list, list) {
        // print the info from the structs to the log
        printk(KERN_INFO "%d, %d %d", ptr->month, ptr->day, ptr->year);
     }
remove_oldest_student();
    return 0;
    }


void simple_exit(void) {
    struct birthday *ptr, *next;
    list_for_each_entry_safe(ptr, next, &birthday_list, list) {
        // delete structs and return memory
        list_del(&ptr->list);
        kfree(ptr);
    }
}

module_init(simple_init);
module_exit(simple_exit);

答案 3 :(得分：1)

context!!.getSystemService(Service.WINDOW_SERVICE) as WindowManager;
相关问题
最新问题