Android example source code file (LabelMaker.java)

This example Android source code file (LabelMaker.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Android by Example" ^TM.

Java - Android tags/keywords

android, arraylist, can't, canvas, convert, drawable, drawing, graphics, illegalargumentexception, label, labelmaker, opengl, paint, rect, state_adding, state_drawing, state_initialized, state_new, string, ui

The LabelMaker.java Android example source code

/*
 * Copyright (C) 2007 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.example.android.apis.graphics.spritetext;

import android.graphics.Bitmap;
import android.graphics.Canvas;
import android.graphics.Paint;
import android.graphics.Rect;
import android.graphics.Paint.Style;
import android.graphics.drawable.Drawable;
import android.opengl.GLUtils;

import java.util.ArrayList;

import javax.microedition.khronos.opengles.GL10;
import javax.microedition.khronos.opengles.GL11;
import javax.microedition.khronos.opengles.GL11Ext;

/**
 * An OpenGL text label maker.
 *
 *
 * OpenGL labels are implemented by creating a Bitmap, drawing all the labels
 * into the Bitmap, converting the Bitmap into an Alpha texture, and drawing
 * portions of the texture using glDrawTexiOES.
 *
 * The benefits of this approach are that the labels are drawn using the high
 * quality anti-aliased font rasterizer, full character set support, and all the
 * text labels are stored on a single texture, which makes it faster to use.
 *
 * The drawbacks are that you can only have as many labels as will fit onto one
 * texture, and you have to recreate the whole texture if any label text
 * changes.
 *
 */
public class LabelMaker {
    /**
     * Create a label maker
     * or maximum compatibility with various OpenGL ES implementations,
     * the strike width and height must be powers of two,
     * We want the strike width to be at least as wide as the widest window.
     *
     * @param fullColor true if we want a full color backing store (4444),
     * otherwise we generate a grey L8 backing store.
     * @param strikeWidth width of strike
     * @param strikeHeight height of strike
     */
    public LabelMaker(boolean fullColor, int strikeWidth, int strikeHeight) {
        mFullColor = fullColor;
        mStrikeWidth = strikeWidth;
        mStrikeHeight = strikeHeight;
        mTexelWidth = (float) (1.0 / mStrikeWidth);
        mTexelHeight = (float) (1.0 / mStrikeHeight);
        mClearPaint = new Paint();
        mClearPaint.setARGB(0, 0, 0, 0);
        mClearPaint.setStyle(Style.FILL);
        mState = STATE_NEW;
    }

    /**
     * Call to initialize the class.
     * Call whenever the surface has been created.
     *
     * @param gl
     */
    public void initialize(GL10 gl) {
        mState = STATE_INITIALIZED;
        int[] textures = new int[1];
        gl.glGenTextures(1, textures, 0);
        mTextureID = textures[0];
        gl.glBindTexture(GL10.GL_TEXTURE_2D, mTextureID);

        // Use Nearest for performance.
        gl.glTexParameterf(GL10.GL_TEXTURE_2D, GL10.GL_TEXTURE_MIN_FILTER,
                GL10.GL_NEAREST);
        gl.glTexParameterf(GL10.GL_TEXTURE_2D, GL10.GL_TEXTURE_MAG_FILTER,
                GL10.GL_NEAREST);

        gl.glTexParameterf(GL10.GL_TEXTURE_2D, GL10.GL_TEXTURE_WRAP_S,
                GL10.GL_CLAMP_TO_EDGE);
        gl.glTexParameterf(GL10.GL_TEXTURE_2D, GL10.GL_TEXTURE_WRAP_T,
                GL10.GL_CLAMP_TO_EDGE);

        gl.glTexEnvf(GL10.GL_TEXTURE_ENV, GL10.GL_TEXTURE_ENV_MODE,
                GL10.GL_REPLACE);
    }

    /**
     * Call when the surface has been destroyed
     */
    public void shutdown(GL10 gl) {
        if ( gl != null) {
            if (mState > STATE_NEW) {
                int[] textures = new int[1];
                textures[0] = mTextureID;
                gl.glDeleteTextures(1, textures, 0);
                mState = STATE_NEW;
            }
        }
    }

    /**
     * Call before adding labels. Clears out any existing labels.
     *
     * @param gl
     */
    public void beginAdding(GL10 gl) {
        checkState(STATE_INITIALIZED, STATE_ADDING);
        mLabels.clear();
        mU = 0;
        mV = 0;
        mLineHeight = 0;
        Bitmap.Config config = mFullColor ?
                Bitmap.Config.ARGB_4444 : Bitmap.Config.ALPHA_8;
        mBitmap = Bitmap.createBitmap(mStrikeWidth, mStrikeHeight, config);
        mCanvas = new Canvas(mBitmap);
        mBitmap.eraseColor(0);
    }

    /**
     * Call to add a label
     *
     * @param gl
     * @param text the text of the label
     * @param textPaint the paint of the label
     * @return the id of the label, used to measure and draw the label
     */
    public int add(GL10 gl, String text, Paint textPaint) {
        return add(gl, null, text, textPaint);
    }

    /**
     * Call to add a label
     *
     * @param gl
     * @param text the text of the label
     * @param textPaint the paint of the label
     * @return the id of the label, used to measure and draw the label
     */
    public int add(GL10 gl, Drawable background, String text, Paint textPaint) {
        return add(gl, background, text, textPaint, 0, 0);
    }

    /**
     * Call to add a label
     * @return the id of the label, used to measure and draw the label
     */
    public int add(GL10 gl, Drawable drawable, int minWidth, int minHeight) {
        return add(gl, drawable, null, null, minWidth, minHeight);
    }

    /**
     * Call to add a label
     *
     * @param gl
     * @param text the text of the label
     * @param textPaint the paint of the label
     * @return the id of the label, used to measure and draw the label
     */
    public int add(GL10 gl, Drawable background, String text, Paint textPaint,
            int minWidth, int minHeight) {
        checkState(STATE_ADDING, STATE_ADDING);
        boolean drawBackground = background != null;
        boolean drawText = (text != null) && (textPaint != null);

        Rect padding = new Rect();
        if (drawBackground) {
            background.getPadding(padding);
            minWidth = Math.max(minWidth, background.getMinimumWidth());
            minHeight = Math.max(minHeight, background.getMinimumHeight());
        }

        int ascent = 0;
        int descent = 0;
        int measuredTextWidth = 0;
        if (drawText) {
            // Paint.ascent is negative, so negate it.
            ascent = (int) Math.ceil(-textPaint.ascent());
            descent = (int) Math.ceil(textPaint.descent());
            measuredTextWidth = (int) Math.ceil(textPaint.measureText(text));
        }
        int textHeight = ascent + descent;
        int textWidth = Math.min(mStrikeWidth,measuredTextWidth);

        int padHeight = padding.top + padding.bottom;
        int padWidth = padding.left + padding.right;
        int height = Math.max(minHeight, textHeight + padHeight);
        int width = Math.max(minWidth, textWidth + padWidth);
        int effectiveTextHeight = height - padHeight;
        int effectiveTextWidth = width - padWidth;

        int centerOffsetHeight = (effectiveTextHeight - textHeight) / 2;
        int centerOffsetWidth = (effectiveTextWidth - textWidth) / 2;

        // Make changes to the local variables, only commit them
        // to the member variables after we've decided not to throw
        // any exceptions.

        int u = mU;
        int v = mV;
        int lineHeight = mLineHeight;

        if (width > mStrikeWidth) {
            width = mStrikeWidth;
        }

        // Is there room for this string on the current line?
        if (u + width > mStrikeWidth) {
            // No room, go to the next line:
            u = 0;
            v += lineHeight;
            lineHeight = 0;
        }
        lineHeight = Math.max(lineHeight, height);
        if (v + lineHeight > mStrikeHeight) {
            throw new IllegalArgumentException("Out of texture space.");
        }

        int u2 = u + width;
        int vBase = v + ascent;
        int v2 = v + height;

        if (drawBackground) {
            background.setBounds(u, v, u + width, v + height);
            background.draw(mCanvas);
        }

        if (drawText) {
            mCanvas.drawText(text,
                    u + padding.left + centerOffsetWidth,
                    vBase + padding.top + centerOffsetHeight,
                    textPaint);
        }

        // We know there's enough space, so update the member variables
        mU = u + width;
        mV = v;
        mLineHeight = lineHeight;
        mLabels.add(new Label(width, height, ascent,
                u, v + height, width, -height));
        return mLabels.size() - 1;
    }

    /**
     * Call to end adding labels. Must be called before drawing starts.
     *
     * @param gl
     */
    public void endAdding(GL10 gl) {
        checkState(STATE_ADDING, STATE_INITIALIZED);
        gl.glBindTexture(GL10.GL_TEXTURE_2D, mTextureID);
        GLUtils.texImage2D(GL10.GL_TEXTURE_2D, 0, mBitmap, 0);
        // Reclaim storage used by bitmap and canvas.
        mBitmap.recycle();
        mBitmap = null;
        mCanvas = null;
    }

    /**
     * Get the width in pixels of a given label.
     *
     * @param labelID
     * @return the width in pixels
     */
    public float getWidth(int labelID) {
        return mLabels.get(labelID).width;
    }

    /**
     * Get the height in pixels of a given label.
     *
     * @param labelID
     * @return the height in pixels
     */
    public float getHeight(int labelID) {
        return mLabels.get(labelID).height;
    }

    /**
     * Get the baseline of a given label. That's how many pixels from the top of
     * the label to the text baseline. (This is equivalent to the negative of
     * the label's paint's ascent.)
     *
     * @param labelID
     * @return the baseline in pixels.
     */
    public float getBaseline(int labelID) {
        return mLabels.get(labelID).baseline;
    }

    /**
     * Begin drawing labels. Sets the OpenGL state for rapid drawing.
     *
     * @param gl
     * @param viewWidth
     * @param viewHeight
     */
    public void beginDrawing(GL10 gl, float viewWidth, float viewHeight) {
        checkState(STATE_INITIALIZED, STATE_DRAWING);
        gl.glBindTexture(GL10.GL_TEXTURE_2D, mTextureID);
        gl.glShadeModel(GL10.GL_FLAT);
        gl.glEnable(GL10.GL_BLEND);
        gl.glBlendFunc(GL10.GL_SRC_ALPHA, GL10.GL_ONE_MINUS_SRC_ALPHA);
        gl.glColor4x(0x10000, 0x10000, 0x10000, 0x10000);
        gl.glMatrixMode(GL10.GL_PROJECTION);
        gl.glPushMatrix();
        gl.glLoadIdentity();
        gl.glOrthof(0.0f, viewWidth, 0.0f, viewHeight, 0.0f, 1.0f);
        gl.glMatrixMode(GL10.GL_MODELVIEW);
        gl.glPushMatrix();
        gl.glLoadIdentity();
        // Magic offsets to promote consistent rasterization.
        gl.glTranslatef(0.375f, 0.375f, 0.0f);
    }

    /**
     * Draw a given label at a given x,y position, expressed in pixels, with the
     * lower-left-hand-corner of the view being (0,0).
     *
     * @param gl
     * @param x
     * @param y
     * @param labelID
     */
    public void draw(GL10 gl, float x, float y, int labelID) {
        checkState(STATE_DRAWING, STATE_DRAWING);
        Label label = mLabels.get(labelID);
        gl.glEnable(GL10.GL_TEXTURE_2D);
        ((GL11)gl).glTexParameteriv(GL10.GL_TEXTURE_2D,
                GL11Ext.GL_TEXTURE_CROP_RECT_OES, label.mCrop, 0);
        ((GL11Ext)gl).glDrawTexiOES((int) x, (int) y, 0,
                (int) label.width, (int) label.height);
    }

    /**
     * Ends the drawing and restores the OpenGL state.
     *
     * @param gl
     */
    public void endDrawing(GL10 gl) {
        checkState(STATE_DRAWING, STATE_INITIALIZED);
        gl.glDisable(GL10.GL_BLEND);
        gl.glMatrixMode(GL10.GL_PROJECTION);
        gl.glPopMatrix();
        gl.glMatrixMode(GL10.GL_MODELVIEW);
        gl.glPopMatrix();
    }

    private void checkState(int oldState, int newState) {
        if (mState != oldState) {
            throw new IllegalArgumentException("Can't call this method now.");
        }
        mState = newState;
    }

    private static class Label {
        public Label(float width, float height, float baseLine,
                int cropU, int cropV, int cropW, int cropH) {
            this.width = width;
            this.height = height;
            this.baseline = baseLine;
            int[] crop = new int[4];
            crop[0] = cropU;
            crop[1] = cropV;
            crop[2] = cropW;
            crop[3] = cropH;
            mCrop = crop;
        }

        public float width;
        public float height;
        public float baseline;
        public int[] mCrop;
    }

    private int mStrikeWidth;
    private int mStrikeHeight;
    private boolean mFullColor;
    private Bitmap mBitmap;
    private Canvas mCanvas;
    private Paint mClearPaint;

    private int mTextureID;

    private float mTexelWidth;  // Convert texel to U
    private float mTexelHeight; // Convert texel to V
    private int mU;
    private int mV;
    private int mLineHeight;
    private ArrayList<Label> mLabels = new ArrayList();

    private static final int STATE_NEW = 0;
    private static final int STATE_INITIALIZED = 1;
    private static final int STATE_ADDING = 2;
    private static final int STATE_DRAWING = 3;
    private int mState;
}