安卓开发笔记，一些有用的方法记录（随时记录）

1、淡入淡出动画的实现

protected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.activity_crossfade);mContentView = findViewById(R.id.content);//要出现的viewmLoadingView = findViewById(R.id.loading_spinner);//要消失的view// Initially hide the content view.mContentView.setVisibility(View.GONE);//先把要出现的view设置为gone,节约内存。// Retrieve and cache the system's default "short" animation time.mShortAnimationDuration = getResources().getInteger(android.R.integer.config_shortAnimTime);//这个变量是系统提供的一种动画时间，他会确保动画执行的更一致和更精致}

private void crossfade() {// Set the content view to 0% opacity but visible, so that it is visible// (but fully transparent) during the animation.mContentView.setAlpha(0f);mContentView.setVisibility(View.VISIBLE);// Animate the content view to 100% opacity, and clear any animation// listener set on the view.mContentView.animate().alpha(1f)//从0到1.setDuration(mShortAnimationDuration).setListener(null);// Animate the loading view to 0% opacity. After the animation ends,// set its visibility to GONE as an optimization step (it won't// participate in layout passes, etc.)mLoadingView.animate().alpha(0f).setDuration(mShortAnimationDuration).setListener(new AnimatorListenerAdapter() {@Overridepublic void onAnimationEnd(Animator animation) {mLoadingView.setVisibility(View.GONE);//在动画的最后要把它设置为gone}});