Android 11 toast居中显示 |
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Android 11以后，系统Toast的text toast被设置为固定在屏幕下方显示，通过setGravity已经不会生效。 为了解决这个问题，去看了Toast源码。从show()方法开始， /** * Show the view for the specified duration. */ public void show() { if (Compatibility.isChangeEnabled(CHANGE_TEXT_TOASTS_IN_THE_SYSTEM)) { checkState(mNextView != null || mText != null, "You must either set a text or a view"); } else { if (mNextView == null) { throw new RuntimeException("setView must have been called"); } } INotificationManager service = getService(); String pkg = mContext.getOpPackageName(); TN tn = mTN; tn.mNextView = mNextView; final int displayId = mContext.getDisplayId(); try { if (Compatibility.isChangeEnabled(CHANGE_TEXT_TOASTS_IN_THE_SYSTEM)) { if (mNextView != null) { // It's a custom toast service.enqueueToast(pkg, mToken, tn, mDuration, displayId); } else { // It's a text toast ITransientNotificationCallback callback = new CallbackBinder(mCallbacks, mHandler); service.enqueueTextToast(pkg, mToken, mText, mDuration, displayId, callback); } } else { service.enqueueToast(pkg, mToken, tn, mDuration, displayId); } } catch (RemoteException e) { // Empty } } 到TN的handleShow()方法， public void handleShow(IBinder windowToken) { if (localLOGV) Log.v(TAG, "HANDLE SHOW: " + this + " mView=" + mView + " mNextView=" + mNextView); // If a cancel/hide is pending - no need to show - at this point // the window token is already invalid and no need to do any work. if (mHandler.hasMessages(CANCEL) || mHandler.hasMessages(HIDE)) { return; } if (mView != mNextView) { // remove the old view if necessary handleHide(); mView = mNextView; mPresenter.show(mView, mToken, windowToken, mDuration, mGravity, mX, mY, mHorizontalMargin, mVerticalMargin, new CallbackBinder(getCallbacks(), mHandler)); } }最终跟踪到ToastPresenter的show()方法， /** * Shows the toast in {@code view} with the parameters passed and callback {@code callback}. */ public void show(View view, IBinder token, IBinder windowToken, int duration, int gravity, int xOffset, int yOffset, float horizontalMargin, float verticalMargin, @Nullable ITransientNotificationCallback callback) { checkState(mView == null, "Only one toast at a time is allowed, call hide() first."); mView = view; mToken = token; adjustLayoutParams(mParams, windowToken, duration, gravity, xOffset, yOffset, horizontalMargin, verticalMargin); if (mView.getParent() != null) { mWindowManager.removeView(mView); } try { mWindowManager.addView(mView, mParams); } catch (WindowManager.BadTokenException e) { // Since the notification manager service cancels the token right after it notifies us // to cancel the toast there is an inherent race and we may attempt to add a window // after the token has been invalidated. Let us hedge against that. Log.w(TAG, "Error while attempting to show toast from " + mPackageName, e); return; } trySendAccessibilityEvent(mView, mPackageName); if (callback != null) { try { callback.onToastShown(); } catch (RemoteException e) { Log.w(TAG, "Error calling back " + mPackageName + " to notify onToastShow()", e); } } }对比android11之前的源码，发现基本没有变动，都是通过WindowManager的addView方法添加toast，而且LayoutParams也有设置Gravity属性， /** * Customizes {@code params} according to other parameters, ready to be passed to {@link * WindowManager#addView(View, ViewGroup.LayoutParams)}. */ private void adjustLayoutParams(WindowManager.LayoutParams params, IBinder windowToken, int duration, int gravity, int xOffset, int yOffset, float horizontalMargin, float verticalMargin) { Configuration config = mResources.getConfiguration(); int absGravity = Gravity.getAbsoluteGravity(gravity, config.getLayoutDirection()); params.gravity = absGravity; if ((absGravity & Gravity.HORIZONTAL_GRAVITY_MASK) == Gravity.FILL_HORIZONTAL) { params.horizontalWeight = 1.0f; } if ((absGravity & Gravity.VERTICAL_GRAVITY_MASK) == Gravity.FILL_VERTICAL) { params.verticalWeight = 1.0f; } params.x = xOffset; params.y = yOffset; params.horizontalMargin = horizontalMargin; params.verticalMargin = verticalMargin; params.packageName = mContext.getPackageName(); params.hideTimeoutMilliseconds = (duration == Toast.LENGTH_LONG) ? LONG_DURATION_TIMEOUT : SHORT_DURATION_TIMEOUT; params.token = windowToken; }但是Gravity属性为什么没有生效呢？ 考虑到是不是Toast的默认view的布局文件设置了match_parent属性，导致Gravity属性不生效。去Toast默认view的布局文件查看（默认view初始化在Toast类的makeText方法里，最终走的是ToastPresenter的getTextToastView方法），果然，发现默认view的布局文件宽高属性，均为match_parent， /** * Make a standard toast to display using the specified looper. * If looper is null, Looper.myLooper() is used. * * @hide */ public static Toast makeText(@NonNull Context context, @Nullable Looper looper, @NonNull CharSequence text, @Duration int duration) { if (Compatibility.isChangeEnabled(CHANGE_TEXT_TOASTS_IN_THE_SYSTEM)) { Toast result = new Toast(context, looper); result.mText = text; result.mDuration = duration; return result; } else { Toast result = new Toast(context, looper); View v = ToastPresenter.getTextToastView(context, text); result.mNextView = v; result.mDuration = duration; return result; } } /** * Returns the default text toast view for message {@code text}. */ public static View getTextToastView(Context context, CharSequence text) { View view = LayoutInflater.from(context).inflate(TEXT_TOAST_LAYOUT, null); TextView textView = view.findViewById(com.android.internal.R.id.message); textView.setText(text); return view; }即虽然我们看到屏幕上的toast只是一个小小的文字部分，但实际其view是布满全局的，这个时候设置gravity就没有任何意义了，因为无论你设置gravity是什么值，view都是铺满全屏的。 解决方案：用到的解决方案就是给toast设置自己的布局文件，当然，自己的布局文件要注意不是铺满全屏的，然后把样式设置成跟系统自带的一样就可以了，此时，设置gravity为Gravity.CENTER就可以生效了（注意，不设置的话，默认还是在屏幕下方），参考代码 Toast toast = new Toast(context); View view = LayoutInflater.from(context).inflate(R.layout.layout_toast, null); //根据自己需要对view设置text或其他样式 toast.setView(view); toast.setGravity(Gravity.CENTER, 0, 0); toast.setDuration(Toast.LENGTH_SHORT); toast.show();参考布局文件 题外话：这次Android11修改toast，不仅把setGravity设置成不可用，还把setView设置成废弃方法了，但实际上我测试发现，无论android11还是android12，调用setView方法后，再设置setGravity还是可以用的，使用默认的setView时不可以用，最终什么时候这个方法不可用无法保证。 2021/08/17 补充：当采用上述的解决方案时，给toast设置的文字内容过长，发现toast会自动换行，但由于我们布局里的高度是写死的，所以会出现换行后部分内容看不见的问题，这里把我的解决方法也放上来。其实解决方法很简单，跟dialog和popupwindow这些类似，就是先计算一遍内容宽高，再把计算好的宽度设置回去，就能一行显示完全（实在一行显示不完就不要用toast了），大体原理还是我们直接inflate的view没有传parent，所以布局的外层属性不会起作用，这就不展开说了，大家可以自己看看源码，下面上解决方法的代码 Toast toast = new Toast(context); View toastView = LayoutInflater.from(context).inflate(R.layout.layout_toast, null); TextView tvMessage = toastView.findViewById(R.id.tv_toast_message); tvMessage.setText(text); tvMessage.measure(View.MeasureSpec.UNSPECIFIED, View.MeasureSpec.UNSPECIFIED); ConstraintLayout.LayoutParams clp = (ConstraintLayout.LayoutParams) tvMessage.getLayoutParams(); clp.width = tvMessage.getMeasuredWidth(); tvMessage.setLayoutParams(clp); toast.setView(toastView); toast.setDuration(Toast.LENGTH_SHORT); |
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