RecyclerView 中的 Android 调色板

Question

我打算从我的RecyclerView 中的每个bitmap 中获取每种鲜艳的颜色，并将其设置为我的文本的背景。所以我尝试了following：

        Picasso.with(ctx)
                .load(curs.getString(curs
                        .getColumnIndex(TimelineDatabase.KEY_IMAGE)))
                .into(holder.ivUserPost, new Callback() {

                    @Override
                    public void onSuccess() {
                        try {
                            Bitmap bitmap = ((BitmapDrawable) holder.ivUserPost
                                    .getDrawable()).getBitmap();
                            Palette palette = Palette.generate(bitmap);
                            Toast.makeText(ctx,
                                    palette.getVibrantColor().getRgb(),
                                    Toast.LENGTH_LONG).show();
                        } catch (Exception e) {
                            e.printStackTrace();
                        }
                    }

但是，没有显示 toast，我不断收到带有following logcat 的 null pointer exception：

07-27 07:13:34.163: W/System.err(4900): java.lang.NullPointerException: Attempt to invoke virtual method 'int android.support.v7.graphics.PaletteItem.getRgb()' on a null object reference
07-27 07:13:34.163: W/System.err(4900):     at com.joy.timeline.Fetch$TimelineFetchAdapter$2.onSuccess(Fetch.java:354)
07-27 07:13:34.163: W/System.err(4900):     at com.squareup.picasso.RequestCreator.into(RequestCreator.java:514)
07-27 07:13:34.163: W/System.err(4900):     at com.joy.timeline.Fetch$TimelineFetchAdapter.onBindViewHolder(Fetch.java:344)
07-27 07:13:34.163: W/System.err(4900):     at com.joy.timeline.Fetch$TimelineFetchAdapter.onBindViewHolder(Fetch.java:1)
07-27 07:13:34.163: W/System.err(4900):     at android.support.v7.widget.RecyclerView$Adapter.bindViewHolder(RecyclerView.java:2925)
07-27 07:13:34.163: W/System.err(4900):     at android.support.v7.widget.RecyclerView$Recycler.getViewForPosition(RecyclerView.java:2527)
07-27 07:13:34.163: W/System.err(4900):     at android.support.v7.widget.LinearLayoutManager$RenderState.next(LinearLayoutManager.java:1425)
07-27 07:13:34.163: W/System.err(4900):     at android.support.v7.widget.LinearLayoutManager.fill(LinearLayoutManager.java:999)
07-27 07:13:34.163: W/System.err(4900):     at android.support.v7.widget.LinearLayoutManager.onLayoutChildren(LinearLayoutManager.java:524)
07-27 07:13:34.163: W/System.err(4900):     at android.support.v7.widget.RecyclerView.dispatchLayout(RecyclerView.java:1461)
07-27 07:13:34.164: W/System.err(4900):     at android.support.v7.widget.RecyclerView.onLayout(RecyclerView.java:1600)
07-27 07:13:34.164: W/System.err(4900):     at android.view.View.layout(View.java:15273)
07-27 07:13:34.164: W/System.err(4900):     at android.view.ViewGroup.layout(ViewGroup.java:4763)
07-27 07:13:34.164: W/System.err(4900):     at android.widget.RelativeLayout.onLayout(RelativeLayout.java:1069)

Answer 1

显然，Palette 在您的位图中找不到鲜艳的颜色。这就是为什么有一个 NPE。您可以尝试让调色板生成更多颜色 - Palette p = Palette.generate(bitmap, 24);。但也不能保证它会找到鲜艳的颜色。

很遗憾，目前还没有官方的Palette 文档。您可以参考this article了解更多信息