在上一篇文章《Android神筆之Paint》學習了Paint的基本用法，但是具體的應用我們還沒有實踐過。從標題中可知，本文是帶領讀者使用Paint，自定義一個進度條控制元件。
上圖就是本文要實現的效果圖。既然是自定義控制元件，本文的該控制元件是直接繼承View，然後重寫View的onMeasure和onDraw方法來實現。其中onMeasure主要作用是測量控制元件的寬/高。而onDraw則是將介面繪製到螢幕上。
從效果的效果上看，我們需要自定義一些屬性，如：進度度條的顏色、圓邊框的顏色、圓邊框的寬度和文字的大小等等。
具體的自定義屬性請看下面attrs.xml的程式碼：
<?xml version="1.0" encoding="utf-8"?>
<resources>
<declare-styleable name="CustomProgressBar">
<attr name="roundProgressColor" format="color"></attr>
<attr name="roundColor" format="color"></attr>
<attr name="roundWidth" format="dimension"></attr>
<attr name="textSize" format="dimension"></attr>
<attr name="textColor" format="color"></attr>
<attr name="max" format="integer"></attr>
<attr name="textShow" format="boolean"></attr>
<attr name="style">
<enum name="STROKE" value="0"></enum>
<enum name="FILL" value="1"></enum>
</attr>
</declare-styleable>
</resources>
複製程式碼接下來看本文的最重要部分，也就是自定義View
public class CustomProgressBar extends View {
private int max = 100;//總進度
private int roundColor = Color.RED;//進度圓弧的顏色
private float roundWidth = 10;//圓邊框寬度
private int roundProgressColor = Color.BLUE;//預設的大圓環邊框顏色
private float textSize = 55;//文字大小
private int textColor = Color.GREEN;//文字預設顏色
private boolean textShow = true;//是否展示文字
public static final int STROKE = 0;//描邊
public static final int FILL = 1;//填充
private int style = STROKE;//預設描邊
private int progress;//進度
private Paint mPaint;
private int mWidth = 200;//預設控制元件寬度，wrap_content時候使用
private int mHeight = 200;//預設控制元件高度，wrap_content時候使用
public CustomProgressBar(Context context) {
this(context, null);
}
public CustomProgressBar(Context context, @Nullable AttributeSet attrs) {
super(context, attrs);
init(context, attrs);
}
private void init(Context context, AttributeSet attrs) {
mPaint = new Paint();
if (attrs != null) {
TypedArray typedArray = context.obtainStyledAttributes(attrs, R.styleable.CustomProgressBar);
max = typedArray.getInteger(R.styleable.CustomProgressBar_max, 100);
roundColor = typedArray.getColor(R.styleable.CustomProgressBar_roundColor, Color.BLUE);
roundProgressColor = typedArray.getColor(R.styleable.CustomProgressBar_roundProgressColor, Color.BLUE);
textColor = typedArray.getColor(R.styleable.CustomProgressBar_textColor, Color.GREEN);
textSize = typedArray.getDimension(R.styleable.CustomProgressBar_textSize, 55);
roundWidth = typedArray.getDimension(R.styleable.CustomProgressBar_roundWidth, 10);
textShow = typedArray.getBoolean(R.styleable.CustomProgressBar_textShow, true);
style = typedArray.getInt(R.styleable.CustomProgressBar_style, 0);
typedArray.recycle();
}
}
@Override
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
super.onMeasure(widthMeasureSpec, heightMeasureSpec);
int widthSpecSize = MeasureSpec.getSize(widthMeasureSpec);
int widthSpecMode = MeasureSpec.getMode(widthMeasureSpec);
int heightSpecSize = MeasureSpec.getSize(heightMeasureSpec);
int heightSpecMode = MeasureSpec.getMode(heightMeasureSpec);
if (widthSpecMode == MeasureSpec.AT_MOST && heightSpecMode == MeasureSpec.AT_MOST){
setMeasuredDimension(mWidth,mHeight);
}else if (widthSpecMode == MeasureSpec.AT_MOST){
setMeasuredDimension(mWidth,heightSpecSize);
}else if (heightSpecMode == MeasureSpec.AT_MOST){
setMeasuredDimension(widthSpecSize,mHeight);
}
}
@Override
protected void onDraw(Canvas canvas) {
super.onDraw(canvas);
final int paddingLeft = getPaddingLeft();
final int paddingRight = getPaddingRight();
final int paddingTop = getPaddingTop();
final int paddingBottom = getPaddingBottom();
int width = getWidth() - paddingLeft - paddingRight;
int height = getHeight() - paddingBottom - paddingTop;
//畫預設的大圓環
float radius = (float)Math.min(width,height)/2.0f;//中心座標點
mPaint.setColor(roundColor);
mPaint.setStyle(Paint.Style.STROKE);//描邊
mPaint.setStrokeWidth(roundWidth);//圓環邊的寬度
// if (style == STROKE){
// mPaint.setStrokeWidth(roundWidth);//圓環邊的寬度
// }
mPaint.setAntiAlias(true);
//(float cx, float cy, float radius, @NonNull Paint paint)
canvas.drawCircle(paddingLeft+width/2,paddingTop+height/2,radius,mPaint);
//畫進度百分比
mPaint.setColor(textColor);
mPaint.setStrokeWidth(0);//圓環的寬度
mPaint.setTextSize(textSize);
mPaint.setTypeface(Typeface.DEFAULT_BOLD);
int percent = (int)(progress/(float)max * 100);
if(textShow && percent!=0 && style == STROKE){
//(@NonNull String text, float x, float y, @NonNull Paint paint)
canvas.drawText(percent+"%", (getWidth()-mPaint.measureText(percent+"%"))/2f,
//y公式： float baselineY = centerY + (fontMetrics.bottom-fontMetrics.top)/2 - fontMetrics.bottom
getWidth()/2f-(mPaint.descent()+mPaint.ascent())/2f,
mPaint);
}
//畫圓弧
//矩形區域，定義圓弧的形狀大小
//(float left, float top, float right, float bottom)
RectF oval = new RectF(paddingLeft, paddingTop, width+paddingLeft, height+paddingTop);
mPaint.setColor(roundProgressColor);
mPaint.setStrokeWidth(roundWidth);//圓環邊的寬度
switch (style){
case STROKE:
mPaint.setStyle(Paint.Style.STROKE);
//(@NonNull RectF oval, float startAngle, float sweepAngle, boolean useCenter,@NonNull Paint paint)
//useCenter:設定圓弧在繪畫的時候，是否經過圓形
canvas.drawArc(oval , 0, 360*progress/max, false, mPaint);
break;
case FILL:
mPaint.setStyle(Paint.Style.FILL_AND_STROKE);
if(progress!=0)
canvas.drawArc(oval , 0, 360*progress/max, true, mPaint);
break;
default:
break;
}
}
public void setProgressWidth(int width) {
mWidth = width;
}
public void setProgressHeight(int height) {
mHeight = height;
}
public synchronized void setMax(int max) {
if (max < 0) {
throw new IllegalArgumentException("max不能小於0");
}
this.max = max;
}
public void setRoundColor(int roundColor) {
this.roundColor = roundColor;
}
public void setRoundWidth(float roundWidth) {
this.roundWidth = roundWidth;
}
public void setRoundProgressColor(int roundProgressColor) {
this.roundProgressColor = roundProgressColor;
}
public void setTextSize(float textSize) {
this.textSize = textSize;
}
public void setTextColor(int textColor) {
this.textColor = textColor;
}
public void setTextShow(boolean textShow) {
this.textShow = textShow;
}
public synchronized void setProgress(int progress) {
if (progress < 0) {
throw new IllegalArgumentException("progress不能小於0");
}
if (progress > max) {
progress = max;
}
if (progress <= max) {
this.progress = progress;
postInvalidate();
}
}
public synchronized int getMax() {
return max;
}
public int getRoundColor() {
return roundColor;
}
public float getRoundWidth() {
return roundWidth;
}
public int getRoundProgressColor() {
return roundProgressColor;
}
public int getTextColor() {
return textColor;
}
public boolean isTextShow() {
return textShow;
}
public synchronized int getProgress() {
return progress;
}
}
複製程式碼流程：初始化的時候會拿到自定義屬性，然後onMeasure方法中測量控制元件的寬和高，該方法主要處理了LayoutParams的wrap_content，當wrap_content時，預設設定預設寬/高，而不是讓控制元件佔據整個螢幕，需要呼叫setMeasuredDimension方法測量。最後測量得到了控制元件的寬/高，呼叫onDraw方法將介面繪製到螢幕上，在onDraw方法繪製的時需要考慮padding的情況，如果不做padding處理，則padding將不起作用。
onDraw繪製流程：先繪製一個預設的大圓環，然後在圓中心繪製百分比的文字，最後再繪製一個進度圓環，進度圓環會覆蓋底部的預設大圓環，這樣就達到顯示進度的情況。
設定好畫筆之後，使用canvas.drawCircle繪製預設的大圓環，再次設定畫筆，使用canvas.drawText方法繪製文字；畫圓弧時需要定義一個矩形區域RectF，通過canvas.drawArc方法繪製。
繪製好之後，如何讓使用者看到進度條在變化呢？其實就是通過setProgress方法裡面的postInvalidate()方法，該方法會重新整理介面，重新整理介面時會呼叫onDraw，這樣就可以將進度畫到螢幕上，進度條不停的在變化。
使用
XML中使用
<?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:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical"
tools:context="com.main.paint.PaintActivity">
<com.main.paint.CustomProgressBar
android:id="@+id/progressbar"
android:layout_width="200dp"
android:layout_height="200dp"
app:roundProgressColor="#FF0000"
app:roundWidth="2dp"
app:textColor="#FF0000"
app:style="STROKE"
android:padding="30dp"
app:textSize="20dp"/>
<com.main.paint.CustomProgressBar
android:id="@+id/progressbar01"
android:layout_width="200dp"
android:layout_height="200dp"
app:roundProgressColor="#FF0000"
app:roundWidth="2dp"
app:textColor="#FF0000"
app:style="FILL"
android:padding="30dp"
app:textSize="20dp"/>
</LinearLayout>
複製程式碼Activity程式碼如下：
public class PaintActivity extends AppCompatActivity {
private CustomProgressBar mCustomProgressBar;
private CustomProgressBar mCustomProgressBar01;
private int progress;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_paint);
mCustomProgressBar = (CustomProgressBar)this.findViewById(R.id.progressbar);
mCustomProgressBar.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
new Thread(new Runnable() {
@Override
public void run() {
progress = 0;
while (progress <= 100) {
progress += 2;
mCustomProgressBar.setProgress(progress);
try {
Thread.sleep(100);
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}
}).start();
}
});
mCustomProgressBar01 = (CustomProgressBar)this.findViewById(R.id.progressbar01);
mCustomProgressBar01.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
new Thread(new Runnable() {
@Override
public void run() {
progress = 0;
while (progress <= 100) {
progress += 2;
mCustomProgressBar01.setProgress(progress);
try {
Thread.sleep(100);
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}
}).start();
}
});
}
}
複製程式碼這樣就完成了一個自定義的進度條控制元件，並且在onDraw方法中使用Paint將介面繪製出來。讀者可以自行實踐一把，加深對Paint的理解。