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轉載請注明出處：http://www.reibang.com/p/b753c4a9ddfa
本文出自 容華謝后的博客
1.寫在前面
SeekBar控件在開發(fā)中還是比較常見的厨钻，比如音視頻進度贮缅、音量調節(jié)等涛漂，但是原生控件有時還不能滿足我們的需求，今天就來學習一下如何自定義SeekBar控件尚蝌，本文主要實現(xiàn)了一個帶文字指示器效果的SeekBar控件，看下最終效果：
IndicatorSeekBar
2.實現(xiàn)
IndicatorSeekBar
public class IndicatorSeekBar extends AppCompatSeekBar {
// 畫筆
private Paint mPaint;
// 進度文字位置信息
private Rect mProgressTextRect = new Rect();
// 滑塊按鈕寬度
private int mThumbWidth = dp2px(50);
// 進度指示器寬度
private int mIndicatorWidth = dp2px(50);
// 進度監(jiān)聽
private OnIndicatorSeekBarChangeListener mIndicatorSeekBarChangeListener;
public IndicatorSeekBar(Context context) {
this(context, null);
}
public IndicatorSeekBar(Context context, AttributeSet attrs) {
this(context, attrs, R.attr.seekBarStyle);
}
public IndicatorSeekBar(Context context, AttributeSet attrs, int defStyleAttr) {
super(context, attrs, defStyleAttr);
init();
}
private void init() {
mPaint = new TextPaint();
mPaint.setAntiAlias(true);
mPaint.setColor(Color.parseColor("#00574B"));
mPaint.setTextSize(sp2px(16));
// 如果不設置padding，當滑動到最左邊或最右邊時魄懂，滑塊會顯示不全
setPadding(mThumbWidth / 2, 0, mThumbWidth / 2, 0);
// 設置滑動監(jiān)聽
this.setOnSeekBarChangeListener(new OnSeekBarChangeListener() {
@Override
public void onProgressChanged(SeekBar seekBar, int progress, boolean fromUser) {
// NO OP
}
@Override
public void onStartTrackingTouch(SeekBar seekBar) {
if (mIndicatorSeekBarChangeListener != null) {
mIndicatorSeekBarChangeListener.onStartTrackingTouch(seekBar);
}
}
@Override
public void onStopTrackingTouch(SeekBar seekBar) {
if (mIndicatorSeekBarChangeListener != null) {
mIndicatorSeekBarChangeListener.onStopTrackingTouch(seekBar);
}
}
});
}
@Override
protected synchronized void onDraw(Canvas canvas) {
super.onDraw(canvas);
String progressText = getProgress() + "%";
mPaint.getTextBounds(progressText, 0, progressText.length(), mProgressTextRect);
// 進度百分比
float progressRatio = (float) getProgress() / getMax();
// thumb偏移量
float thumbOffset = (mThumbWidth - mProgressTextRect.width()) / 2 - mThumbWidth * progressRatio;
float thumbX = getWidth() * progressRatio + thumbOffset;
float thumbY = getHeight() / 2f + mProgressTextRect.height() / 2f;
canvas.drawText(progressText, thumbX, thumbY, mPaint);
if (mIndicatorSeekBarChangeListener != null) {
float indicatorOffset = getWidth() * progressRatio - (mIndicatorWidth - mThumbWidth) / 2 - mThumbWidth * progressRatio;
mIndicatorSeekBarChangeListener.onProgressChanged(this, getProgress(), indicatorOffset);
}
}
/**
* 設置進度監(jiān)聽
*
* @param listener OnIndicatorSeekBarChangeListener
*/
public void setOnSeekBarChangeListener(OnIndicatorSeekBarChangeListener listener) {
this.mIndicatorSeekBarChangeListener = listener;
}
/**
* 進度監(jiān)聽
*/
public interface OnIndicatorSeekBarChangeListener {
/**
* 進度監(jiān)聽回調
*
* @param seekBar SeekBar
* @param progress 進度
* @param indicatorOffset 指示器偏移量
*/
public void onProgressChanged(SeekBar seekBar, int progress, float indicatorOffset);
/**
* 開始拖動
*
* @param seekBar SeekBar
*/
public void onStartTrackingTouch(SeekBar seekBar);
/**
* 停止拖動
*
* @param seekBar SeekBar
*/
public void onStopTrackingTouch(SeekBar seekBar);
}
/**
* dp轉px
*
* @param dp dp值
* @return px值
*/
public int dp2px(float dp) {
return (int) TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_DIP, dp,
getResources().getDisplayMetrics());
}
/**
* sp轉px
*
* @param sp sp值
* @return px值
*/
private int sp2px(float sp) {
return (int) TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_SP, sp,
getResources().getDisplayMetrics());
}
}
重點看下onDraw方法：
@Override
protected synchronized void onDraw(Canvas canvas) {
super.onDraw(canvas);
String progressText = getProgress() + "%";
mPaint.getTextBounds(progressText, 0, progressText.length(), mProgressTextRect);
// 進度百分比
float progressRatio = (float) getProgress() / getMax();
// thumb偏移量
float thumbOffset = (mThumbWidth - mProgressTextRect.width()) / 2 - mThumbWidth * progressRatio;
float thumbX = getWidth() * progressRatio + thumbOffset;
float thumbY = getHeight() / 2f + mProgressTextRect.height() / 2f;
canvas.drawText(progressText, thumbX, thumbY, mPaint);
if (mIndicatorSeekBarChangeListener != null) {
float indicatorOffset = getWidth() * progressRatio - (mIndicatorWidth - mThumbWidth) / 2 - mThumbWidth * progressRatio;
mIndicatorSeekBarChangeListener.onProgressChanged(this, getProgress(), indicatorOffset);
}
}
再看一遍效果圖：
IndicatorSeekBar
可以看到，進度百分比文字是跟著進度變化在平移的闯第，所以X軸坐標根據(jù)進度動態(tài)計算就可以了【總寬度 * 進度百分比】（getWidth() * progressRatio）市栗，文字需要居中顯示，所以需要向右平移【（滑塊寬度 - 文字寬度）/ 2】（(mThumbWidth - mProgressTextRect.width()) / 2）咳短。
為了避免滑塊滑動到終點時布局被隱藏填帽，需要為SeekBar設置左右padding，距離分別為滑塊寬度的一半咙好，篡腌，所以【控件總長度 = 控件實際長度 + 滑塊寬度】，向右平移的過程中就要動態(tài)減去滑塊寬度【滑塊寬度 * 進度百分比】（mThumbWidth * progressRatio）勾效，到這里文字的X軸坐標就計算完成了嘹悼。
文字在平移的過程中始終是垂直居中的，所以Y軸坐標可以這樣計算【控件高度 / 2 + 文字高度 / 2】（getHeight() / 2f + mProgressTextRect.height() / 2f）层宫，注意drawText方法默認是從左下角開始繪制文字的杨伙，如果對繪制文字還不太了解，可以看下這篇文章《Android 圖解Canvas drawText文字居中的那些事》
指示器跟隨滑塊移動
在IndicatorSeekBar中萌腿，向外提供了一個setOnSeekBarChangeListener方法用來回調SeekBar的狀態(tài)限匣，其中onProgressChanged方法中的indicatorOffset參數(shù)就是指示器控件的X坐標，計算方式與上文中進度百分比文字的計算方式一致：
// 【總寬度 * 進度百分比 -（指示器寬度 - 滑塊寬度）/ 2 - 滑塊寬度 * 進度百分比】
float indicatorOffset = getWidth() * progressRatio - (mIndicatorWidth - mThumbWidth) / 2 - mThumbWidth * progressRatio;
mIndicatorSeekBarChangeListener.onProgressChanged(this, getProgress(), indicatorOffset);
看下如何使用：
public class MainActivity extends AppCompatActivity {
private TextView tvIndicator;
private IndicatorSeekBar indicatorSeekBar;
private Paint mPaint = new Paint();
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
tvIndicator = findViewById(R.id.tv_indicator);
indicatorSeekBar = findViewById(R.id.indicator_seek_bar);
initData();
}
private void initData() {
final LinearLayout.LayoutParams params = (LinearLayout.LayoutParams) tvIndicator.getLayoutParams();
indicatorSeekBar.setOnSeekBarChangeListener(new IndicatorSeekBar.OnIndicatorSeekBarChangeListener() {
@Override
public void onProgressChanged(SeekBar seekBar, int progress, float indicatorOffset) {
String indicatorText = progress + "%";
tvIndicator.setText(indicatorText);
params.leftMargin = (int) indicatorOffset;
tvIndicator.setLayoutParams(params);
}
@Override
public void onStartTrackingTouch(SeekBar seekBar) {
tvIndicator.setVisibility(View.VISIBLE);
}
@Override
public void onStopTrackingTouch(SeekBar seekBar) {
tvIndicator.setVisibility(View.INVISIBLE);
}
});
}
}
布局文件：
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent">
<LinearLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_centerInParent="true"
android:layout_marginStart="20dp"
android:layout_marginEnd="20dp"
android:orientation="vertical">
<TextView
android:id="@+id/tv_indicator"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:background="@drawable/bg_indicator"
android:gravity="center"
android:textColor="#FFFFFF"
android:textSize="16sp"
android:visibility="invisible" />
<com.yl.indicatorseekbar.IndicatorSeekBar
android:id="@+id/indicator_seek_bar"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_marginTop="5dp"
android:background="@null"
android:max="100"
android:maxHeight="2dp"
android:minHeight="2dp"
android:progress="50"
android:progressDrawable="@drawable/seekbar_progress_drawable"
android:thumb="@drawable/seekbar_thumb" />
</LinearLayout>
</RelativeLayout>
3.寫在最后
代碼已上傳至GitHub哮奇，歡迎Star膛腐、Fork睛约！
GitHub地址：https://github.com/alidili/Demos/tree/master/IndicatorSeekBarDemo
本文Demo的Apk下載地址：https://github.com/alidili/Demos/raw/master/IndicatorSeekBarDemo/IndicatorSeekBarDemo.apk
