Android触屏事件处理策略

在frameworks/base/libs/androidfw/VelocityTracker.cpp VelocityTrackerStrategy* VelocityTracker::createStrategy(const char* strategy) { if (!strcmp("lsq1", strategy)) { // 1st order least squares. Quality: POOR. // Frequently underfits the touch data especially when the finger accelerates // or changes direction. Often underestimates velocity. The direction // is overly influenced by historical touch points. return new LeastSquaresVelocityTrackerStrategy(1); } if (!strcmp("lsq2", strategy)) { // 2nd order least squares. Quality: VERY GOOD. // Pretty much ideal, but can be confused by certain kinds of touch data, // particularly if the panel has a tendency to generate delayed, // duplicate or jittery touch coordinates when the finger is released. return new LeastSquaresVelocityTrackerStrategy(2); } if (!strcmp("lsq3", strategy)) { // 3rd order least squares. Quality: UNUSABLE. // Frequently overfits the touch data yielding wildly divergent estimates // of the velocity when the finger is released. return new LeastSquaresVelocityTrackerStrategy(3); } if (!strcmp("wlsq2-delta", strategy)) { // 2nd order weighted least squares, delta weighting. Quality: EXPERIMENTAL return new LeastSquaresVelocityTrackerStrategy(2, LeastSquaresVelocityTrackerStrategy::WEIGHTING_DELTA); } if (!strcmp("wlsq2-central", strategy)) { // 2nd order weighted least squares, central weighting. Quality: EXPERIMENTAL return new LeastSquaresVelocityTrackerStrategy(2, LeastSquaresVelocityTrackerStrategy::WEIGHTING_CENTRAL); } if (!strcmp("wlsq2-recent", strategy)) { // 2nd order weighted least squares, recent weighting. Quality: EXPERIMENTAL return new LeastSquaresVelocityTrackerStrategy(2, LeastSquaresVelocityTrackerStrategy::WEIGHTING_RECENT); } if (!strcmp("int1", strategy)) { // 1st order integrating filter. Quality: GOOD. // Not as good as 'lsq2' because it cannot estimate acceleration but it is // more tolerant of errors. Like 'lsq1', this strategy tends to underestimate // the velocity of a fling but this strategy tends to respond to changes in // direction more quickly and accurately. return new IntegratingVelocityTrackerStrategy(1); } if (!strcmp("int2", strategy)) { // 2nd order integrating filter. Quality: EXPERIMENTAL. // For comparison purposes only. Unlike 'int1' this strategy can compensate // for acceleration but it typically overestimates the effect. return new IntegratingVelocityTrackerStrategy(2); } if (!strcmp("legacy", strategy)) { // Legacy velocity tracker algorithm. Quality: POOR. // For comparison purposes only. This algorithm is strongly influenced by // old data points, consistently underestimates velocity and takes a very long // time to adjust to changes in direction. return new LegacyVelocityTrackerStrategy(); } return NULL; }
默认策略是： const char* VelocityTracker::DEFAULT_STRATEGY = "lsq2";
可通过 property "debug.velocitytracker.strategy" 修改。如修改为lsq1 。这个需要和kernel中的TP驱动一起调试， lsq2是最优效果，表示上报的速度是一个抛物线；lsq1上报的速度是一个加速度直线。这个需要和kernel上报一致。才能触动流畅。
VelocityTracker::VelocityTracker(const char* strategy) : mLastEventTime(0), mCurrentPointerIdBits(0), mActivePointerId(-1) { char value[PROPERTY_VALUE_MAX]; // Allow the default strategy to be overridden using a system property for debugging. if (!strategy) { int length = property_get("debug.velocitytracker.strategy", value, NULL); if (length > 0) { strategy = value; } else { strategy = DEFAULT_STRATEGY; } } // Configure the strategy. if (!configureStrategy(strategy)) { ALOGD("Unrecognized velocity tracker strategy name '%s'.", strategy); if (!configureStrategy(DEFAULT_STRATEGY)) { LOG_ALWAYS_FATAL("Could not create the default velocity tracker strategy '%s'!", strategy); } } }

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