Android应用中怎么实现一个长按图片保存功能

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监听图片加载的loaddingview源码

package com.leo.camerroll;

import android.animation.ValueAnimator;
import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.graphics.RectF;
import android.util.AttributeSet;
import android.util.TypedValue;
import android.view.View;
import android.view.animation.Animation;
import android.view.animation.LinearInterpolator;
import android.widget.ProgressBar;

/**
 * Created by leo on 17/1/22.
 */

public class LoadingView extends ProgressBar {
  private final int DEFAULT_RADIUS = dp2px(15);
  private final int DEFAULT_REACH_COLOR = 0XFFFFFFFF;
  private final int DEFAULT_UNREACH_COLOR = 0X88000000;
  private final long ANIM_DURATION = 1000;
  private final String BASE_TEXT = "00%";
  private boolean isStop;

  private int mRadius = DEFAULT_RADIUS;
  private int mStrokeWidth;
  private Paint reachPaint;
  private Paint unreachPaint;
  private Paint textPaint;
  private Paint bgPaint;

  private int mStartAngle=0;
  private float mSweepAngle=360*0.382f;

  private ValueAnimator anim;

  public LoadingView(Context context) {
    this(context, null);
  }

  public LoadingView(Context context, AttributeSet attrs) {
    this(context, attrs, 0);
  }

  public LoadingView(Context context, AttributeSet attrs, int defStyleAttr) {
    super(context, attrs, defStyleAttr);
    initView();
  }

  private void initView() {
    reachPaint = new Paint(Paint.ANTI_ALIAS_FLAG | Paint.DITHER_FLAG);
    reachPaint.setStrokeCap(Paint.Cap.ROUND);
    reachPaint.setStyle(Paint.Style.STROKE);
    unreachPaint = new Paint(reachPaint);
    reachPaint.setColor(DEFAULT_REACH_COLOR);
    unreachPaint.setColor(DEFAULT_UNREACH_COLOR);
    textPaint = new Paint(Paint.ANTI_ALIAS_FLAG | Paint.DITHER_FLAG);
    textPaint.setStyle(Paint.Style.STROKE);
    textPaint.setColor(Color.WHITE);
    textPaint.setFakeBoldText(true);

    bgPaint=new Paint(Paint.ANTI_ALIAS_FLAG|Paint.DITHER_FLAG);
    bgPaint.setStrokeCap(Paint.Cap.ROUND);
    bgPaint.setColor(Color.argb(44,0,0,0));
    setMax(100);
  }

  @Override
  protected synchronized void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
    int defWidth = resolveSize(getSuggestedMinimumWidth(), widthMeasureSpec);
    int defHeight = resolveSize(getSuggestedMinimumHeight(), heightMeasureSpec);
    int expectSize = Math.min(defHeight, defWidth);
    if (expectSize <= 0) {
      expectSize = mRadius * 2;
    } else {
      mRadius = expectSize / 2;
    }
    mStrokeWidth = mRadius / 5;
    reachPaint.setStrokeWidth(mStrokeWidth);
    unreachPaint.setStrokeWidth(mStrokeWidth);

    setMeasuredDimension(expectSize, expectSize);

    float textSize=0;
    while(true){
      textSize+=0.1;
      textPaint.setTextSize(textSize);
      if(textPaint.measureText(BASE_TEXT,0,BASE_TEXT.length())>=mRadius){
        break;
      }
    }
  }

  @Override
  protected synchronized void onDraw(Canvas canvas) {
    if(isStop){
      setVisibility(View.GONE);
      return;
    }
    //drawbackground transparent
    canvas.drawCircle(getWidth()/2,getWidth()/2,mRadius-mStrokeWidth,bgPaint);
    //draw reach
    drawProgressReach(canvas);
    //draw progress text
    drawProgressText(canvas);
  }

  private void drawProgressText(Canvas canvas) {
    String text=String.valueOf((int)(getProgress()*1.0f/getMax()*100))+"%";
    int centerX=getWidth()/2;
    int centerY=getWidth()/2;
    int baseX= (int) (centerX-textPaint.measureText(text,0,text.length())/2);
    int baseY= (int) (centerY-(textPaint.getFontMetrics().ascent+textPaint.getFontMetrics().descent)/2);
    canvas.drawText(text,baseX,baseY,textPaint);
  }

  private void drawProgressReach(Canvas canvas) {
    canvas.drawArc(new RectF(0 + mStrokeWidth / 2, 0 + mStrokeWidth / 2, mRadius * 2 - mStrokeWidth / 2, mRadius * 2 - mStrokeWidth / 2), mStartAngle, mSweepAngle, false, reachPaint);
    //drawonreach
    canvas.drawArc(new RectF(0 + mStrokeWidth / 2, 0 + mStrokeWidth / 2, mRadius * 2 - mStrokeWidth / 2, mRadius * 2 - mStrokeWidth / 2), mStartAngle+mSweepAngle, 360-mSweepAngle,false, unreachPaint);
  }

  @Override
  protected void onAttachedToWindow() {
    super.onAttachedToWindow();
    if(anim==null){
      anim=ValueAnimator.ofInt(0,360);
      anim.setInterpolator(new LinearInterpolator());
      anim.setDuration(ANIM_DURATION);
      anim.setRepeatCount(Animation.INFINITE);
      anim.addUpdateListener(new ValueAnimator.AnimatorUpdateListener() {
        @Override
        public void onAnimationUpdate(ValueAnimator animation) {
          if(animation!=null&&animation.getAnimatedValue()!=null){
            int startAngle= (int) animation.getAnimatedValue();
            mStartAngle=startAngle;
            postInvalidate();
          }
        }
      });
    }else{
      anim.cancel();
      anim.removeAllUpdateListeners();
    }
    anim.start();
  }

  public void loadCompleted() {
    isStop=true;
    if(anim!=null){
      anim.cancel();
      anim.removeAllUpdateListeners();
      this.setVisibility(View.GONE);
    }
  }

  /**
   * @param size
   * @return px
   */
  private int dp2px(int size) {
    return (int) TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_DIP, size, getContext().getResources().getDisplayMetrics());
  }
}

实现起来还是很简单的，就是动态改变两端弧的起点和终点，通过属性动画不断的在（0－360）循环，代码应该还算比较清晰哈！～～～～

图片加载用了一个AsyncTask:

private class DownImageTask extends AsyncTask {
    private ImageView imageView;
    private long contentLength;
    public DownImageTask(ImageView imageView) {
      this.imageView = imageView;
    }

    @Override
    protected Bitmap doInBackground(String... params) {
      Bitmap bitmap = null;
      BufferedInputStream bis = null;
      ByteArrayOutputStream bos = null;
      try {
        File fileDir=new File(getApplication().getExternalCacheDir(),"images");
        if(fileDir==null||!fileDir.isDirectory()){
          fileDir.mkdir();
        }
        File file=new File(fileDir.getAbsolutePath()+"/"+params[0].hashCode()+".png");
        if(file!=null&&file.length()>0){
          return bitmap=BitmapFactory.decodeFile(file.getAbsolutePath());
        }
        bos=new ByteArrayOutputStream();
        byte[] buffer = new byte[512];
        long total=0;
        int len ;
        URL url = new URL(params[0]);
        HttpURLConnection conn = (HttpURLConnection) url.openConnection();
        this.contentLength = conn.getContentLength();
        bis = new BufferedInputStream(conn.getInputStream());
        while ((len = bis.read(buffer)) != -1) {
          total+=len;
          publishProgress(total);
          Thread.sleep(100);
          bos.write(buffer, 0, len);
          bos.flush();
        }
        bitmap= BitmapFactory.decodeByteArray(bos.toByteArray(),0,bos.toByteArray().length);
        saveBitmapToDisk(bos,params[0]);
      } catch (Exception e) {
        e.printStackTrace();
      } finally {
        try {
          if (bis != null) {
            bis.close();
          }
          if (bos != null) {
            bos.close();
          }
        } catch (IOException e) {
          e.printStackTrace();
        }
      }
      return bitmap;
    }

    private void saveBitmapToDisk(final ByteArrayOutputStream baos, final String url) {
      new Thread(){
        @Override
        public void run() {BufferedOutputStream bos=null;
          try{
            if(!Environment.MEDIA_MOUNTED.equals(Environment.getExternalStorageState())){
              Log.e("TAG","内存卡不存在");
              return;
            }
            Log.e("TAG","开始保存图片至内存卡～～");
            byte[] bytes = baos.toByteArray();
            File fileDir=new File(getApplication().getExternalCacheDir(),"images");
            if(fileDir==null||!fileDir.isDirectory()){
              fileDir.mkdir();
            }
            File file=new File(fileDir.getAbsolutePath()+"/"+url.hashCode()+".png");
            file.createNewFile();
            bos=new BufferedOutputStream(new FileOutputStream(file));
            bos.write(bytes);
            bos.flush();
            Log.e("TAG","图片已经保存至内存卡～～");
          }catch (Exception e){
            e.printStackTrace();
          }finally {
            if(bos!=null){
              try {
                bos.close();
              } catch (IOException e) {
                e.printStackTrace();
              }
            }
          }
        }
      }.start();
    }

    @Override
    protected void onProgressUpdate(Long... values) {
      mLoadingView.setProgress((int) ((values[0].longValue() * 1.0f / contentLength) * 100));
    }

    @Override
    protected void onPostExecute(Bitmap bitmap) {
      if (imageView != null && bitmap != null) {
        imageView.setImageBitmap(bitmap);
        mLoadingView.loadCompleted();
      }
    }
  }

加载完毕后把图片存放在了内存卡中（当然，这是我随便写的一个图片加载，大家换成自己的加载框架哈，）：

private void saveBitmapToDisk(final ByteArrayOutputStream baos, final String url) {
      new Thread(){
        @Override
        public void run() {BufferedOutputStream bos=null;
          try{
            if(!Environment.MEDIA_MOUNTED.equals(Environment.getExternalStorageState())){
              Log.e("TAG","内存卡不存在");
              return;
            }
            Log.e("TAG","开始保存图片至内存卡～～");
            byte[] bytes = baos.toByteArray();
            File fileDir=new File(getApplication().getExternalCacheDir(),"images");
            if(fileDir==null||!fileDir.isDirectory()){
              fileDir.mkdir();
            }
            File file=new File(fileDir.getAbsolutePath()+"/"+url.hashCode()+".png");
            file.createNewFile();
            bos=new BufferedOutputStream(new FileOutputStream(file));
            bos.write(bytes);
            bos.flush();
            Log.e("TAG","图片已经保存至内存卡～～");
          }catch (Exception e){
            e.printStackTrace();
          }finally {
            if(bos!=null){
              try {
                bos.close();
              } catch (IOException e) {
                e.printStackTrace();
              }
            }
          }
        }
      }.start();
    }

这里我们是需要把图片保存到内存卡中，所以考虑到了android 6.0的运行时权限，所以小伙伴们也一定要判断哦，我在oncreate的时候就判断了：

if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
      if (ContextCompat.checkSelfPermission(this, Manifest.permission.WRITE_EXTERNAL_STORAGE)
          != PackageManager.PERMISSION_GRANTED) {
        requestAlertWindowPermission();
      }
    }

private static final int REQUEST_CODE = 1;
  private void requestAlertWindowPermission() {
    ActivityCompat.requestPermissions(this,new String[]{Manifest.permission.WRITE_EXTERNAL_STORAGE},REQUEST_CODE);
  }

下面就是讲长按图片保存至相册了：

 mImageView.setOnLongClickListener(new View.OnLongClickListener(){
      @Override
      public boolean onLongClick(View v) {
        if(mImageView.getDrawable() instanceof BitmapDrawable){
          Toast.makeText(getApplicationContext(),"长按保存图片至相册",Toast.LENGTH_SHORT).show();
          File fileDir=new File(getApplication().getExternalCacheDir(),"images");
          File file=new File(fileDir.getAbsolutePath()+"/"+IMAGE_URL.hashCode()+".png");
          if(file!=null&&file.length()>0){
            CameraRollManager rollManager=new CameraRollManager(MainActivity.this, Uri.parse(file.getAbsolutePath()));
            rollManager.execute();
          }
        }
        return false;
      }
    });

CameraRollManager是我直接copy的reactnatvie中的android模块的代码：

CameraRollManager.java

package com.leo.camerroll.camera;

import android.content.Context;
import android.content.Intent;
import android.media.MediaScannerConnection;
import android.net.Uri;
import android.os.Environment;
import android.os.Handler;
import android.os.Looper;
import android.os.Message;
import android.widget.Toast;

import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.nio.channels.FileChannel;

/**
 * Created by leo on 17/1/22.
 */

public class CameraRollManager extends GuardedAsyncTask{
  private static Context mContext;
  private final Uri mUri;
  private static Handler handler=new Handler(Looper.getMainLooper()){
    @Override
    public void handleMessage(Message msg) {
      Toast.makeText(mContext,"保存成功！",Toast.LENGTH_SHORT).show();
      Intent intent = new Intent();
      intent.setType("image/*");
      intent.setAction(Intent.ACTION_GET_CONTENT);
      mContext.startActivity(intent);
    }
  };
  public CameraRollManager(Context context, Uri uri) {
    super(context);
    mContext = context;
    mUri = uri;
  }

  @Override
  protected void doInBackgroundGuarded(Object[] params) {
    File source = new File(mUri.getPath());
    FileChannel input = null, output = null;
    try {
      File exportDir = Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_PICTURES);
      exportDir.mkdirs();
      if (!exportDir.isDirectory()) {
        return;
      }
      File dest = new File(exportDir, source.getName());
      int n = 0;
      String fullSourceName = source.getName();
      String sourceName, sourceExt;
      if (fullSourceName.indexOf('.') >= 0) {
        sourceName = fullSourceName.substring(0, fullSourceName.lastIndexOf('.'));
        sourceExt = fullSourceName.substring(fullSourceName.lastIndexOf('.'));
      } else {
        sourceName = fullSourceName;
        sourceExt = "";
      }
      while (!dest.createNewFile()) {
        dest = new File(exportDir, sourceName + "_" + (n++) + sourceExt);
      }
      input = new FileInputStream(source).getChannel();
      output = new FileOutputStream(dest).getChannel();
      output.transferFrom(input, 0, input.size());
      input.close();
      output.close();

      MediaScannerConnection.scanFile(
          mContext,
          new String[]{dest.getAbsolutePath()},
          null,
          new MediaScannerConnection.OnScanCompletedListener() {
            @Override
            public void onScanCompleted(String path, Uri uri) {
              handler.sendEmptyMessage(0);
            }
          });
    } catch (IOException e) {
    } finally {
      if (input != null && input.isOpen()) {
        try {
          input.close();
        } catch (IOException e) {
        }
      }
      if (output != null && output.isOpen()) {
        try {
          output.close();
        } catch (IOException e) {
        }
      }
    }
  }
}

GuardedAsyncTask.java:

package com.leo.camerroll.camera;

import android.content.Context;
import android.os.AsyncTask;

/**
 * Created by leo on 17/1/22.
 */

public abstract class GuardedAsyncTask 
    extends AsyncTask {

  private final Context mReactContext;

  protected GuardedAsyncTask(Context reactContext) {
    mReactContext = reactContext;
  }

  @Override
  protected final Void doInBackground(Params... params) {
    try {
      doInBackgroundGuarded(params);
    } catch (RuntimeException e) {
    }
    return null;
  }

  protected abstract void doInBackgroundGuarded(Params... params);
}

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