Android 中查找 native 方法及虚线的实现
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在上一篇中简单提了一下(http://blog.pingfangx.com/2385.html)
```
android.graphics.drawable.GradientDrawable#inflate
android.graphics.drawable.GradientDrawable#inflateChildElements
android.graphics.drawable.GradientDrawable#updateGradientDrawableStroke
android.graphics.drawable.GradientDrawable#setStroke(int, android.content.res.ColorStateList, float, float)
android.graphics.drawable.GradientDrawable#setStrokeInternal
DashPathEffect e = null;
if (dashWidth > 0) {
e = new DashPathEffect(new float[] { dashWidth, dashGap }, 0);
}
mStrokePaint.setPathEffect(e);
public class DashPathEffect extends PathEffect {
public DashPathEffect(float intervals[], float phase) {
if (intervals.length < 2) {
throw new ArrayIndexOutOfBoundsException();
}
native_instance = nativeCreate(intervals, phase);
}
private static native long nativeCreate(float intervals[], float phase);
}
public class PathEffect {
protected void finalize() throws Throwable {
nativeDestructor(native_instance);
native_instance = 0;// Other finalizers can still call us.
}
private static native void nativeDestructor(long native_patheffect);
long native_instance;
}
到了 native 不知道怎么继续了，于是今天查一下。
参考(http://blog.csdn.net/hp910315/article/details/51733410)
他转自(http://gityuan.com/2016/05/28/android-jni/)
方法名android.graphics.DashPathEffect#nativeCreate
转android_graphics_DashPathEffect#nativeCreate
在/framework/base/core/jni/中搜索DashPathEffect
定位到frameworks/base/core/jni/android/graphics/PathEffect.cpp
android::RegisterMethodsOrDie(env, "android/graphics/DashPathEffect", gDashPathEffectMethods,
NELEM(gDashPathEffectMethods));
然后是
static const JNINativeMethod gDashPathEffectMethods[] = {
{ "nativeCreate", "([FF)J", (void*)SkPathEffectGlue::Dash_constructor }
};
然后是
frameworks/base/core/jni/android/graphics/PathEffect.cpp
class SkPathEffectGlue {
...
static jlong Dash_constructor(JNIEnv* env, jobject,
jfloatArray intervalArray, jfloat phase) {
AutoJavaFloatArray autoInterval(env, intervalArray);
int count = autoInterval.length() & ~1;// even number
#ifdef SK_SCALAR_IS_FLOAT
SkScalar* intervals = autoInterval.ptr();
#else
#error Need to convert float array to SkScalar array before calling the following function.
#endif
SkPathEffect* effect = SkDashPathEffect::Make(intervals, count, phase).release();
return reinterpret_cast<jlong>(effect);
}
}
接下来Make方法
external/skia/src/effects/SkDashPathEffect.cpp
sk_sp<SkPathEffect> SkDashPathEffect::Make(const SkScalar intervals[], int count, SkScalar phase) {
if (!SkDashPath::ValidDashPath(phase, intervals, count)) {
return nullptr;
}
return sk_sp<SkPathEffect>(new SkDashPathEffect(intervals, count, phase));
}
构造函数
SkDashPathEffect::SkDashPathEffect(const SkScalar intervals[], int count, SkScalar phase)
: fPhase(0)
, fInitialDashLength(-1)
, fInitialDashIndex(0)
, fIntervalLength(0) {
SkASSERT(intervals);
SkASSERT(count > 1 && SkIsAlign2(count));
fIntervals = (SkScalar*)sk_malloc_throw(sizeof(SkScalar) * count);
fCount = count;
for (int i = 0; i < count; i++) {
fIntervals = intervals;
}
// set the internal data members
SkDashPath::CalcDashParameters(phase, fIntervals, fCount,
&fInitialDashLength, &fInitialDashIndex, &fIntervalLength, &fPhase);
}
CalcDashParameters
external/skia/src/utils/SkDashPath.cpp
void SkDashPath::CalcDashParameters(SkScalar phase, const SkScalar intervals[], int32_t count,
SkScalar* initialDashLength, int32_t* initialDashIndex,
SkScalar* intervalLength, SkScalar* adjustedPhase) {
SkScalar len = 0;
for (int i = 0; i < count; i++) {
len += intervals;
}
*intervalLength = len;
// Adjust phase to be between 0 and len, "flipping" phase if negative.
// e.g., if len is 100, then phase of -20 (or -120) is equivalent to 80
if (adjustedPhase) {
if (phase < 0) {
phase = -phase;
if (phase > len) {
phase = SkScalarMod(phase, len);
}
phase = len - phase;
// Due to finite precision, it's possible that phase == len,
// even after the subtract (if len >>> phase), so fix that here.
// This fixes http://crbug.com/124652 .
SkASSERT(phase <= len);
if (phase == len) {
phase = 0;
}
} else if (phase >= len) {
phase = SkScalarMod(phase, len);
}
*adjustedPhase = phase;
}
SkASSERT(phase >= 0 && phase < len);
*initialDashLength = find_first_interval(intervals, phase,
initialDashIndex, count);
SkASSERT(*initialDashLength >= 0);
SkASSERT(*initialDashIndex >= 0 && *initialDashIndex < count);
}
static SkScalar find_first_interval(const SkScalar intervals[], SkScalar phase,
int32_t* index, int count) {
for (int i = 0; i < count; ++i) {
SkScalar gap = intervals;
if (phase > gap || (phase == gap && gap)) {
phase -= gap;
} else {
*index = i;
return gap - phase;
}
}
// If we get here, phase "appears" to be larger than our length. This
// shouldn't happen with perfect precision, but we can accumulate errors
// during the initial length computation (rounding can make our sum be too
// big or too small. In that event, we just have to eat the error here.
*index = 0;
return intervals;
}
```
好了，到此，我们应该能找到是怎么创建 DashPathEffect 的了，但是问题来了，自己对底层这一块不熟悉，还是不知道怎么画出来的。
所以，还是需要下一篇（也许多年后吧）……
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