安卓裁剪系统自带的图片的这些参数去哪里查阅？

例如下面这段代码，putExtra这里面的参数是怎么寻找的啊？小白求解释

 public void clipPhoto(Uri uri) {

        Intent intent = new Intent("com.android.camera.action.CROP");
        //可以选择图片类型，如果是*表明所有类型的图片
        intent.setDataAndType(uri, "image/*");
        // 下面这个crop = true是设置在开启的Intent中设置显示的VIEW可裁剪
        intent.putExtra("crop", "true");
        // aspectX aspectY 是宽高的比例，这里设置的是正方形（长宽比为1:1）
        intent.putExtra("aspectX", 1);
        intent.putExtra("aspectY", 1);
        // outputX outputY 是裁剪图片宽高
        intent.putExtra("outputX", 1000);
        intent.putExtra("outputY", 1000);
        //裁剪时是否保留图片的比例，这里的比例是1:1
        intent.putExtra("scale", true);
        //是否是圆形裁剪区域，设置了也不一定有效
        //intent.putExtra("circleCrop", true);
        //设置输出的格式
        intent.putExtra("outputFormat", Bitmap.CompressFormat.JPEG.toString());
        //是否将数据保留在Bitmap中返回
        intent.putExtra("return-data", true);

        startActivityForResult(intent, CUT_OK);
    }

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这段代码调用的是系统的图片裁剪类，有兴趣可去看系统裁剪器源码

/packages/apps/Gallery2/src/com/android/gallery3d/filltershow/crop/CropActivity.java

这个Activity接收处理"com.android.camera.action.CROP"的Action，里边有个方法

    protected static CropExtras getExtrasFromIntent(Intent intent) {
        Bundle extras = intent.getExtras();
        if (extras != null) {
            return new CropExtras(extras.getInt(CropExtras.KEY_OUTPUT_X, 0),
                    extras.getInt(CropExtras.KEY_OUTPUT_Y, 0),
                    extras.getBoolean(CropExtras.KEY_SCALE, true) &&
                            extras.getBoolean(CropExtras.KEY_SCALE_UP_IF_NEEDED, false),
                    extras.getInt(CropExtras.KEY_ASPECT_X, 0),
                    extras.getInt(CropExtras.KEY_ASPECT_Y, 0),
                    extras.getBoolean(CropExtras.KEY_SET_AS_WALLPAPER, false),
                    extras.getBoolean(CropExtras.KEY_RETURN_DATA, false),
                    (Uri) extras.getParcelable(MediaStore.EXTRA_OUTPUT),
                    extras.getString(CropExtras.KEY_OUTPUT_FORMAT),
                    extras.getBoolean(CropExtras.KEY_SHOW_WHEN_LOCKED, false),
                    extras.getFloat(CropExtras.KEY_SPOTLIGHT_X),
                    extras.getFloat(CropExtras.KEY_SPOTLIGHT_Y));
        }
        return null;
    }

再来看CropExtras类

/packages/apps/Gallery2/src/com/android/gallery3d/filltershow/crop/CropExtras.java

里边定义了常量

public static final String KEY_CROPPED_RECT = "cropped-rect";
    public static final String KEY_OUTPUT_X = "outputX";
    public static final String KEY_OUTPUT_Y = "outputY";
    public static final String KEY_SCALE = "scale";
    public static final String KEY_SCALE_UP_IF_NEEDED = "scaleUpIfNeeded";
    public static final String KEY_ASPECT_X = "aspectX";
    public static final String KEY_ASPECT_Y = "aspectY";
    public static final String KEY_SET_AS_WALLPAPER = "set-as-wallpaper";
    public static final String KEY_RETURN_DATA = "return-data";
    public static final String KEY_DATA = "data";
    public static final String KEY_SPOTLIGHT_X = "spotlightX";
    public static final String KEY_SPOTLIGHT_Y = "spotlightY";
    public static final String KEY_SHOW_WHEN_LOCKED = "showWhenLocked";
    public static final String KEY_OUTPUT_FORMAT = "outputFormat";