import definition = require("fps-meter/fps-native");

export class FPSCallback implements definition.FPSCallback {

private impl: android.view.Choreographer.FrameCallback;

private onFrame: (currentTimeMillis: number) => void;

public running: boolean;

constructor(onFrame: (currentTimeMillis: number) => void) {

this.running = false;

this.onFrame = onFrame;

this.impl = new android.view.Choreographer.FrameCallback({

doFrame: (nanos: number) => {

this.handleFrame(nanos);

}

});

}

public start() {

if (this.running) {

return;

}

android.view.Choreographer.getInstance().postFrameCallback(this.impl);

this.running = true;

}

public stop() {

if (!this.running) {

return;

}

android.view.Choreographer.getInstance().removeFrameCallback(this.impl);

this.running = false;

}

private handleFrame(nanos: number) {

if (!this.running) {

return;

}

// divide by 1 000 000 since the parameter is in nanoseconds

this.onFrame(nanos / 1000000);

// add the FrameCallback instance again since it is automatically removed from the Choreographer

android.view.Choreographer.getInstance().postFrameCallback(this.impl);

}

}