使用 Glide 将位图加载到 ImageView [英] Using Glide to load bitmap into ImageView

问题描述

如何使用 Glide 库将位图加载到我的 ImageView 中?我想创建一个带有文本的自定义图像，并使用 Glide 将其加载到 imageview 中.

这是我用文本创建自定义位图的方法

public Bitmap imageWithText(String text) {TextView tv = new TextView(context);tv.setText(文本);tv.setTextColor(Color.WHITE);tv.setBackgroundColor(Color.BLACK);tv.setTypeface(null, Typeface.BOLD);tv.setGravity(Gravity.CENTER);tv.setTextSize(20);tv.setPadding(0, 25, 0, 0);位图 testB = Bitmap.createBitmap(100, 100, Bitmap.Config.ARGB_8888);画布 c = 新画布(testB)；tv.layout(0, 0, 100, 100);tv.draw(c);返回测试B；}

但是当我尝试使用 glide 加载此位图时，出现错误

Glide.with(getContext()).load(imageWithText("Random text")).into(holder.imgPhoto);

解决方案

注意它如何加载前几个项目，然后逐渐加载其余项目.内存缓存和池预热需要一点时间，但如果您想要更流畅的显示，您可以使用预加载器.加热后，它滚动得很好.操作栏上的删除按钮调用 Glide.clearDiskCache() 和 Glide.clearMemory() 以便它再次开始重新生成项目.

How can i use Glide library to load Bitmap into my ImageView? I want to create a custom image with text and load it into imageview using Glide.

This is my method to create custom bitmap with text

public Bitmap imageWithText(String text) {
    TextView tv = new TextView(context);
    tv.setText(text);
    tv.setTextColor(Color.WHITE);
    tv.setBackgroundColor(Color.BLACK);
    tv.setTypeface(null, Typeface.BOLD);
    tv.setGravity(Gravity.CENTER);
    tv.setTextSize(20);
    tv.setPadding(0, 25, 0, 0);
    Bitmap testB = Bitmap.createBitmap(100, 100, Bitmap.Config.ARGB_8888);
    Canvas c = new Canvas(testB);
    tv.layout(0, 0, 100, 100);
    tv.draw(c);
    return testB;
}

But when i try to load this bitmap using glide i'm getting error

Glide.with(getContext()).load(imageWithText("Random text")).into(holder.imgPhoto);

解决方案

@rookiedev is right, there's no load(Bitmap) in Glide, for a reason: acquiring a Bitmap usually takes time and sometimes blocking I/O. So it's not good practice to call imageWithText on the UI thread. Update: That being said I proposed this feature a while back; and while the hacks are easier to do you can find the "Glide way" below, which I highly recommend.

Glide is designed to be flexible and this problem demonstrates that trait extremely well. The following implementation may seem long, but all pieces have their reason for existence. Given the performance gain, this amount of code to fit your generator into Glide's world is not much. I tried to format it to be short, collapsing irrelevant parts and using static imports to be shorter (see the end for imports).

The code also includes programmatically generated UI so you can just copy-paste all the below code into GlideGeneratedImageListFragment.java and run it; the only external dependency is support lib's RecyclerView.

class GeneratingAdapter extends RecyclerView.Adapter<RecyclerView.ViewHolder> {
    // See https://docs.google.com/drawings/d/1KyOJkNd5Dlm8_awZpftzW7KtqgNR6GURvuF6RfB210g/edit?usp=sharing
    //                                  ModelType/A,    DataType/T,     ResourceType/Z, TranscodeType/R
    private final GenericRequestBuilder<GenerateParams, GenerateParams, Bitmap,         GlideDrawable> generator;

    public GeneratingAdapter(final Context context) {
        generator = Glide // this part should be cleaner in Glide 4.0, but that's not released yet
        .with(context)
        .using(new GenerateParamsPassthroughModelLoader(), GenerateParams.class)          // custom class
        .from(GenerateParams.class)
        .as(Bitmap.class)
        .transcode(new BitmapToGlideDrawableTranscoder(context), GlideDrawable.class)     // builtin
        .decoder(new GenerateParamsBitmapResourceDecoder(context))                        // custom class
        .encoder(new BitmapEncoder(Bitmap.CompressFormat.PNG, 0/*ignored for lossless*/)) // builtin
        .cacheDecoder(new FileToStreamDecoder<Bitmap>(new StreamBitmapDecoder(context)))  // builtin
        //.placeholder(new ColorDrawable(Color.YELLOW)) // you can pre-set placeholder and error
        .error(new ColorDrawable(Color.RED))            // so it's easier when binding
        //.diskCacheStrategy(DiskCacheStrategy.NONE)    // only for debugging to always regenerate
        //.skipMemoryCache(true)                        // only for debugging to always regenerate
        ;
    }
    @Override public int getItemCount() { return 1000; }

    private final float[] colorCache = new float[] {0, 1.0f, 0.5f};
    private final float[] bgCache = new float[] {0, 0.5f, 1.0f};
    @Override public void onBindViewHolder(RecyclerView.ViewHolder holder, int position) {
        colorCache[0] = bgCache[0] = (position * 15) % 360; // just to have a fancy example :)
        GenerateParams params = new GenerateParams(
                // omit position to see Glide caching in action (every 24th item / 12th row is the same)
                "android text"/* + " #" + position*/,
                Color.HSVToColor(colorCache),
                Color.HSVToColor(bgCache)
        );
        generator/*.clone() in case you see weird behavior*/.load(params).into((ImageView)holder.itemView);
    }

    @Override public RecyclerView.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
        int height = parent.getContext().getResources().getDisplayMetrics().heightPixels / 3;
        ImageView view = new ImageView(parent.getContext());
        view.setLayoutParams(new RecyclerView.LayoutParams(MATCH_PARENT, height));
        view.setScaleType(ImageView.ScaleType.FIT_CENTER);
        return new RecyclerView.ViewHolder(view) {}; // anon class for brevity
    }
}

public class GlideGeneratedImageListFragment extends Fragment {
    @Override public @Nullable View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        RecyclerView view = new RecyclerView(container.getContext());
        view.setLayoutParams(new MarginLayoutParams(MATCH_PARENT, MATCH_PARENT));
        view.setLayoutManager(new GridLayoutManager(container.getContext(), 2 /*columns*/));
        view.setAdapter(new GeneratingAdapter(view.getContext()));
        return view;
    }
}

/** Extracted params from imageWithText, but left some hardcoded values like 20sp/bold/center in {@link Generators}. */
class GenerateParams {
    final String text;
    final int color;
    final int background;

    public GenerateParams(String text, int color, int bg) {
        this.text = text;
        this.color = color;
        this.background = bg;
    }

    public String getId() {
        // TODO make sure it's unique for every possible instance of GenerateParams
        // because it will affect how the resulting bitmap is cached
        // the below is correct correct for the current fields, if those change this has to change
        return String.format(Locale.ROOT, "%s-%08x-%08x", text, color, background);
    }
}

/** Boilerplate because of the degeneration in ModelType == DataType, but important for caching.
 *  @see GeneratingAdapter#generator */
class GenerateParamsPassthroughModelLoader implements ModelLoader<GenerateParams, GenerateParams> {
    @Override public DataFetcher<GenerateParams> getResourceFetcher(final GenerateParams model, int width, int height) {
        return new DataFetcher<GenerateParams>() {
            @Override public GenerateParams loadData(Priority priority) throws Exception { return model; }
            @Override public void cleanup() { }
            @Override public String getId() { return model.getId(); }
            @Override public void cancel() { }
        };
    }
}

/** Handles pooling to reduce/prevent GC lagging from too many {@link Bitmap#createBitmap}s */
class GenerateParamsBitmapResourceDecoder implements ResourceDecoder<GenerateParams, Bitmap> {
    private final Context context;
    public GenerateParamsBitmapResourceDecoder(Context context) { this.context = context; }
    @Override public Resource<Bitmap> decode(GenerateParams source, int width, int height) throws IOException {
        BitmapPool pool = Glide.get(context).getBitmapPool();
        Bitmap bitmap = pool.getDirty(width, height, Bitmap.Config.ARGB_8888);
        if (bitmap == null) {
            bitmap = Bitmap.createBitmap(width, height, Bitmap.Config.ARGB_8888);
        }
        Generators.imageWithTextNoLayout(context, bitmap, source);
        return BitmapResource.obtain(bitmap, pool);
    }
    @Override public String getId() {
        // be careful if you change the Generator implementation you have to change this
        // otherwise the users may see a cached image; or clear cache on app update
        return "com.example.MyImageGenerator";
    }
}

class Generators {
    /** OP's original implementation fixed for real centering */
    public static Bitmap imageWithText(Context context, Bitmap bitmap, GenerateParams params) {
        TextView view = new TextView(context);
        view.setText(params.text);
        view.setTextColor(params.color);
        view.setBackgroundColor(params.background);
        view.setTypeface(null, Typeface.BOLD);
        view.setGravity(Gravity.CENTER);
        view.setTextSize(20 /*sp*/);
        Canvas canvas = new Canvas(bitmap);
        view.measure(makeMeasureSpec(canvas.getWidth(), EXACTLY), makeMeasureSpec(canvas.getHeight(), EXACTLY));
        view.layout(0, 0, canvas.getWidth(), canvas.getHeight());
        view.draw(canvas);
        return bitmap;
    }

    /** Generate centered text without creating a View, more lightweight.
     * Consider https://stackoverflow.com/a/8369690/253468 for multiline support. */
    public static Bitmap imageWithTextNoLayout(Context context, Bitmap bitmap, GenerateParams params) {
        Paint paint = new Paint();
        paint.setColor(params.color);
        paint.setTextAlign(Paint.Align.CENTER); // text's anchor for the x given in drawText
        paint.setTextSize(applyDimension(COMPLEX_UNIT_SP, 20, context.getResources().getDisplayMetrics()));
        paint.setTypeface(Typeface.DEFAULT_BOLD);

        Canvas canvas = new Canvas(bitmap);
        canvas.drawColor(params.background);
        canvas.drawText(params.text, canvas.getWidth() / 2, canvas.getHeight() / 2, paint);
        return bitmap;
    }
}

// Here are the imports in case you need it;
// didn't want to put it in the beginning to keep the relevant code first.

import java.io.IOException;
import java.util.Locale;

import android.content.Context;
import android.graphics.*;
import android.graphics.drawable.ColorDrawable;
import android.os.Bundle;
import android.support.annotation.Nullable;
import android.support.v4.app.Fragment;
import android.support.v7.widget.*;
import android.view.*;
import android.view.ViewGroup.MarginLayoutParams;
import android.widget.*;

import static android.util.TypedValue.*;
import static android.view.View.MeasureSpec.*;
import static android.view.ViewGroup.LayoutParams.*;

import com.bumptech.glide.*;
import com.bumptech.glide.load.ResourceDecoder;
import com.bumptech.glide.load.data.DataFetcher;
import com.bumptech.glide.load.engine.Resource;
import com.bumptech.glide.load.engine.bitmap_recycle.BitmapPool;
import com.bumptech.glide.load.model.ModelLoader;
import com.bumptech.glide.load.resource.bitmap.*;
import com.bumptech.glide.load.resource.drawable.GlideDrawable;
import com.bumptech.glide.load.resource.file.FileToStreamDecoder;
import com.bumptech.glide.load.resource.transcode.BitmapToGlideDrawableTranscoder;

Here's how it looks like (real scrolling is much smoother, GIF is really low FPS):

Notice how it loads the first few items and then gradually loads the rest. It takes a little that the memory cache and pool warms up, but you can use a preloader if you want even smoother display. After it's warmed up it scrolls nicely. The delete button on the action bar calls Glide.clearDiskCache() and Glide.clearMemory() so it starts regenating the items again.

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