Android实现字幕滚动程序并优化

  Android实现字幕滚动，不使用内置的属性，而是重新定义一个类继承自AppCompatTextView来实现，可以控制文字滚动速度且让其匀速滚动，首先定义一个方法得到屏幕宽度和文本长度

public void scrollTextView(WindowManager windowManager, String text) {
        // 获取画笔paint
        paint = this.getPaint();
        //paint.setColor(Color.BLACK);
        //使用抗锯齿效果，使文本更加平滑
        paint.setSubpixelText(true);
        paint.setAntiAlias(true);
        //设置文字大小和颜色
        paint.setTextSize(50);
        this.setTextColor(Color.BLACK);
        // 得到文字
        this.text = text;
        textLength = paint.measureText(text);// 获得当前文本字符串长度
        viewWidth = this.getWidth();// 获取view的宽度;
        if (viewWidth == 0) {
            if (windowManager != null) {
                // 获取当前屏幕的属性
                Display display = windowManager.getDefaultDisplay();
                Point size = new Point();
                display.getSize(size);
                viewWidth = size.x;// 获取屏幕宽度
            }
        }
        xPos = textLength;
        currentLength = viewWidth + textLength;
        changeLength = viewWidth + textLength * 2;// 使文字到最左边
        // 文字的大小+距顶部的距离
        yPos = this.getTextSize() + this.getPaddingTop();
    }

  重写onDraw方法

@Override
    protected void onDraw(Canvas canvas) {
        /**
         * 两次进入onDraw函数的时间间隔
         */
        time1 =System.currentTimeMillis();
        if (time2!=0){
        timeDesc=time1-time2;
        }
        speed=getSpeed();
        TIME=getTIME();
        //文字从最右边开始滚动
        if (isStarting) {
            canvas.drawColor(Color.WHITE);
            canvas.drawText(text, currentLength - xPos, yPos, paint);
            //每次滚动速度
            if (timeDesc!=0){
                if (TIME!=0){
                xPos += speed/TIME*timeDesc;//根据时间差计算滚动距离
                }
                else {
                    xPos =xPos+ 0;
                }
            }
            else {
                xPos += speed;
            }
            // 当文字滚动到屏幕的最左边
            if (xPos >= changeLength) {//最后一个文字到达最左边时
                // 把文字设置到最右边开始
                xPos = currentLength - viewWidth;
            }

        }
        time2 = time1;
        super.onDraw(canvas);
    }

然后在MainActivity中实现一个定时器，控制刷新时间

Handler handler = new Handler();
    Runnable runnable = new Runnable() {
        @Override
        public void run() {
            // handler自带方法实现定时器
            try {
                handler.postDelayed(this, TIME);
                marquee.invalidate();

            } catch (Exception e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
        }
    };

MainActivity中的onCreate方法控制刷新时间和速度

protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        marquee = (MarqueeView) findViewById(R.id.scrollView);
        //设置刷新时间
        timeChange = (EditText) findViewById(R.id.time_text1);
        timeButton = (Button) findViewById(R.id.time_button1);
        timeButton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                timeText = timeChange.getText().toString();
                try {
                    timeTxt = Integer.parseInt(timeText);
                    if (timeTxt != 0) {
                        marquee.setTIME(timeTxt);
                    } else {
                        marquee.setTIME(0);
                        Log.i("speed", speedChange.getText() + "");
                    }
                } catch (Exception e) {
                    marquee.setTIME(0);
                    //marquee.setSpeed(0);
                    Log.i("speed", speedChange.getText() + "");
                }
            }
        });

        //设置滚动速度
        speedChange = (EditText) findViewById(R.id.speed_text1);
        speedButton = (Button) findViewById(R.id.speed_button1);
        speedButton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                speedText = speedChange.getText().toString();
                try {
                    speedTxt = Integer.parseInt(speedText);
                    if (speedTxt != 0) {
                        marquee.setSpeed(speedTxt);
                        Log.i("speed", speedChange.getText() + "");
                    } else {
                        marquee.setSpeed(0);
                    }
                } catch (Exception e) {
                    marquee.setTIME(3);
                    marquee.setSpeed(0);
                }
            }
        });
        //intent所附带的额外数据
        String path = this.getIntent().getStringExtra("path");
        if (path != null) {
            marquee.scrollTextView(this.getWindowManager(),
                    path);
            marquee.startScroll();
        } else {
            marquee.scrollTextView(this.getWindowManager(),
                    "AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA");
            marquee.startScroll();
        }
        handler.postDelayed(runnable, TIME);
    }

在activity_main中需定义一个自定义控件，两个button和两个EditText，自定义控件需要标注完整的包名。

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/linearLayout"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    tools:context="com.sun.scrollwords.MainActivity">
    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content">
        <com.sun.scrollwords.MarqueeView
            android:id="@+id/scrollview"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:background="#CCCCCC"
            android:ellipsize="marquee"
            android:singleLine="true"
            android:textColor="#000000"
            android:textSize="50sp" />
    </LinearLayout>
    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content">
        <EditText
            android:id="@+id/time_text1"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:hint="刷新时间是13"
            android:maxLines="1"
            android:textSize="30sp" />
        <Button
            android:id="@+id/time_button1"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="更改时间"
            android:textSize="30sp" />
    </LinearLayout>
        <LinearLayout
            android:layout_width="match_parent"
            android:layout_height="wrap_content">
        <EditText
            android:id="@+id/speed_text1"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:hint="速度为3"
            android:maxLines="1"
            android:textSize="30sp" />
        <Button
            android:id="@+id/speed_button1"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="更改速度"
            android:textSize="30sp" />
        </LinearLayout>
</LinearLayout>

以上代码可以控制速度和刷新时间，为了进一步优化程序，可以将文字转变为图片格式，这样不用每次都计算文字的位置，可以减少CPU的占用率。将文字转为图片格式的方法为：

public static Bitmap textToBitmap(String text, int textSize) {
        TextPaint textPaint = new TextPaint();
        textPaint.setColor(Color.BLACK);
        //使用抗锯齿效果，使文本更加平滑
        textPaint.setSubpixelText(true);
        textPaint.setAntiAlias(true);
        textPaint.setTextSize(textSize);
        textLen = textPaint.measureText(text);
        //textLen是文本的宽度，必须以文本宽度分割，否则文本过长时会导致换行
        StaticLayout layout = new StaticLayout(text, textPaint, Math.round(textLen),
                Layout.Alignment.ALIGN_NORMAL, 1.3f, 0.0f, true);
        Bitmap bitmap = Bitmap.createBitmap(layout.getWidth() + 10,
                layout.getHeight() + 10, Bitmap.Config.ARGB_8888);
        Canvas canvas = new Canvas(bitmap);
        canvas.translate(10, 10);
        canvas.drawColor(Color.WHITE);
        layout.draw(canvas);
        return bitmap;
    }

然后需要实现图片自动滚动，定义方法startMarquee,并使用ValueAnimator创建过程并不断更新位置

public void startMarquee(int startLeft, int startTop, int toLeft, int toTop, long duration) {
        mStartLeft = startLeft;
        mStartTop = startTop;
        mToLeft = toLeft;
        mToTop = toTop;
        // 使用ValueAnimator创建一个过程
        ValueAnimator valueAnimator = ValueAnimator.ofFloat(0, 1);
        valueAnimator.setDuration(duration);
       //使图片匀速滚动
        valueAnimator.setInterpolator(new LinearInterpolator());
        valueAnimator.addUpdateListener(new ValueAnimator.AnimatorUpdateListener() {
           @Override
            public void onAnimationUpdate(ValueAnimator animator) {
                // 不断重新计算上下左右位置
                float fraction = (Float) animator.getAnimatedValue();
                int currentLeft = (int) ((mToLeft - mStartLeft) * fraction + mStartLeft);
                int currentTop = (int) ((mToTop - mStartTop) * fraction + mStartTop);
                if (mDestRect == null) {
                    mDestRect = new Rect(currentLeft, currentTop, currentLeft + mBitWidth,
                            currentTop + mBitHeight);
                }
                mDestRect.left = currentLeft;
                mDestRect.right = currentLeft + mBitWidth;
                mDestRect.top = currentTop;
                mDestRect.bottom = currentTop + mBitHeight;
                Log.i("currentLeft", currentLeft + "");
            }
        });
        valueAnimator.setRepeatCount(valueAnimator.INFINITE);
        valueAnimator.setRepeatMode(ValueAnimator.RESTART);
        valueAnimator.start();
    }
public void startMarquee() {
        startTranslate(screenWidth, 0, -mBitWidth, 0, 3500);

    }

在MainActivity中实现调用，并实现定时器决定刷新时间间隔

public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        drawBitmapView = new DrawBitmapView(this);
        setContentView(drawBitmapView, new ActionBar.LayoutParams(ActionBar.LayoutParams.MATCH_PARENT,
                ActionBar.LayoutParams.MATCH_PARENT));
        drawBitmapView.startMarquee();
        handler2.postDelayed(runnable2, TIME2);
        }
    Handler handler2 = new Handler();
    Runnable runnable2 = new Runnable() {
        @Override
        public void run() {
            // handler自带方法实现定时器
            try {
                handler2.postDelayed(this, TIME2);
                try {
                    drawBitmapView.invalidate();
                    Log.i("TIME", System.currentTimeMillis() + "");
                } catch (NullPointerException e) {
                    e.printStackTrace();
                }
            } catch (Exception e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
                Log.i("runnable", "exception... ");
            }
        }
    };

如果需要在界面添加EditText和Button，由于布局是手动加载完成的，所以添加控件也需要Java代码实现，最后的onCreate代码如下：

public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        RelativeLayout myLayout = new RelativeLayout(this);
        myLayout.setBackgroundColor(Color.WHITE);
        drawBitmapView = new BitmapView(this);

        timeButton2 = new Button(this);
        timeButton2.setText("更改刷新时间");
        timeText2= new EditText(this);
        timeText2.setHint("刷新时间为13");
        //为空间设置ID,需要在res/values下新建一个文件，添加控件id
        timeButton2.setId(R.id.timeButton2);
        timeText2.setId(R.id.timeText2);
        drawBitmapView.setId(R.id.drawBitmapView);
        //定义好父容器并设置相关属性
        final RelativeLayout.LayoutParams bitmapParams =
                new RelativeLayout.LayoutParams(
                        RelativeLayout.LayoutParams.WRAP_CONTENT,
                        RelativeLayout.LayoutParams.WRAP_CONTENT);
        bitmapParams.addRule(RelativeLayout.BELOW,timeButton2.getId());
        bitmapParams.addRule(RelativeLayout.CENTER_HORIZONTAL);

        //设置Button的布局参数
        RelativeLayout.LayoutParams buttonParams =
                new RelativeLayout.LayoutParams(
                        RelativeLayout.LayoutParams.WRAP_CONTENT,
                        RelativeLayout.LayoutParams.WRAP_CONTENT);

        buttonParams.addRule(RelativeLayout.CENTER_VERTICAL);
        buttonParams.addRule(RelativeLayout.CENTER_HORIZONTAL);
        //设置EditText的布局参数
        RelativeLayout.LayoutParams speedParams =
                new RelativeLayout.LayoutParams(
                        RelativeLayout.LayoutParams.WRAP_CONTENT,
                        RelativeLayout.LayoutParams.WRAP_CONTENT);

        speedParams.addRule(RelativeLayout.LEFT_OF, timeButton2.getId());
        speedParams.addRule(RelativeLayout.ALIGN_TOP,timeButton2.getId());

        //将布局添加到父容器中
        myLayout.addView(drawBitmapView, bitmapParams);
        myLayout.addView(timeButton2, buttonParams);
        myLayout.addView(timeText2,speedParams);
  
        //设置显示父容器
        setContentView(myLayout);
        timeButton2.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                timeTxt2 = timeText2.getText().toString();
                try {
                     time2= Integer.parseInt(timeTxt2);
                    if (time2 != 0) {
                        TIME2=time2;
                    } else {
                        TIME2=0;
                    }
                } catch (Exception e) {
                    TIME2=0;
                }
            }
        });
        drawBitmapView.startMarquee();
        handler2.postDelayed(runnable2, TIME2);
    }
  
    Handler handler2 = new Handler();
    Runnable runnable2 = new Runnable() {
        @Override
        public void run() {
            // handler自带方法实现定时器
            try {

                handler2.postDelayed(this, TIME2);
                try {
                    drawBitmapView.invalidate();
                              } catch (NullPointerException e) {
                    e.printStackTrace();
                }
            } catch (Exception e) {
                    e.printStackTrace();
                           }
        }
    }；