Java tutorial
/* * Copyright (C) 2014 The Android Open Source Project * * Licensed under the Apache License, Version 2.0 (the "License"); * you may not use this file except in compliance with the License. * You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */ package android.support.v7.app; import android.content.Context; import android.content.ContextWrapper; import android.content.res.TypedArray; import android.os.Build; import android.support.annotation.NonNull; import android.support.annotation.Nullable; import android.support.v4.util.ArrayMap; import android.support.v4.view.ViewCompat; import android.support.v7.appcompat.R; import android.support.v7.view.ContextThemeWrapper; import android.support.v7.widget.AppCompatAutoCompleteTextView; import android.support.v7.widget.AppCompatButton; import android.support.v7.widget.AppCompatCheckBox; import android.support.v7.widget.AppCompatCheckedTextView; import android.support.v7.widget.AppCompatEditText; import android.support.v7.widget.AppCompatImageButton; import android.support.v7.widget.AppCompatImageView; import android.support.v7.widget.AppCompatMultiAutoCompleteTextView; import android.support.v7.widget.AppCompatRadioButton; import android.support.v7.widget.AppCompatRatingBar; import android.support.v7.widget.AppCompatSeekBar; import android.support.v7.widget.AppCompatSpinner; import android.support.v7.widget.AppCompatTextView; import android.support.v7.widget.TintContextWrapper; import android.util.AttributeSet; import android.util.Log; import android.view.InflateException; import android.view.View; import java.lang.reflect.Constructor; import java.lang.reflect.InvocationTargetException; import java.lang.reflect.Method; import java.util.Map; /** * This class is responsible for manually inflating our tinted widgets which are used on devices * running {@link android.os.Build.VERSION_CODES#KITKAT KITKAT} or below. As such, this class * should only be used when running on those devices. * <p>This class two main responsibilities: the first is to 'inject' our tinted views in place of * the framework versions in layout inflation; the second is backport the {@code android:theme} * functionality for any inflated widgets. This include theme inheritance from it's parent. */ class AppCompatViewInflater { private static final Class<?>[] sConstructorSignature = new Class[] { Context.class, AttributeSet.class }; private static final int[] sOnClickAttrs = new int[] { android.R.attr.onClick }; private static final String[] sClassPrefixList = { "android.widget.", "android.view.", "android.webkit." }; private static final String LOG_TAG = "AppCompatViewInflater"; private static final Map<String, Constructor<? extends View>> sConstructorMap = new ArrayMap<>(); private final Object[] mConstructorArgs = new Object[2]; public final View createView(View parent, final String name, @NonNull Context context, @NonNull AttributeSet attrs, boolean inheritContext, boolean readAndroidTheme, boolean readAppTheme, boolean wrapContext) { final Context originalContext = context; // We can emulate Lollipop's android:theme attribute propagating down the view hierarchy // by using the parent's context if (inheritContext && parent != null) { context = parent.getContext(); } if (readAndroidTheme || readAppTheme) { // We then apply the theme on the context, if specified context = themifyContext(context, attrs, readAndroidTheme, readAppTheme); } if (wrapContext) { context = TintContextWrapper.wrap(context); } View view = null; // We need to 'inject' our tint aware Views in place of the standard framework versions switch (name) { case "TextView": view = new AppCompatTextView(context, attrs); break; case "ImageView": view = new AppCompatImageView(context, attrs); break; case "Button": view = new AppCompatButton(context, attrs); break; case "EditText": view = new AppCompatEditText(context, attrs); break; case "Spinner": view = new AppCompatSpinner(context, attrs); break; case "ImageButton": view = new AppCompatImageButton(context, attrs); break; case "CheckBox": view = new AppCompatCheckBox(context, attrs); break; case "RadioButton": view = new AppCompatRadioButton(context, attrs); break; case "CheckedTextView": view = new AppCompatCheckedTextView(context, attrs); break; case "AutoCompleteTextView": view = new AppCompatAutoCompleteTextView(context, attrs); break; case "MultiAutoCompleteTextView": view = new AppCompatMultiAutoCompleteTextView(context, attrs); break; case "RatingBar": view = new AppCompatRatingBar(context, attrs); break; case "SeekBar": view = new AppCompatSeekBar(context, attrs); break; } if (view == null && originalContext != context) { // If the original context does not equal our themed context, then we need to manually // inflate it using the name so that android:theme takes effect. view = createViewFromTag(context, name, attrs); } if (view != null) { // If we have created a view, check it's android:onClick checkOnClickListener(view, attrs); } return view; } private View createViewFromTag(Context context, String name, AttributeSet attrs) { if (name.equals("view")) { name = attrs.getAttributeValue(null, "class"); } try { mConstructorArgs[0] = context; mConstructorArgs[1] = attrs; if (-1 == name.indexOf('.')) { for (int i = 0; i < sClassPrefixList.length; i++) { final View view = createView(context, name, sClassPrefixList[i]); if (view != null) { return view; } } return null; } else { return createView(context, name, null); } } catch (Exception e) { // We do not want to catch these, lets return null and let the actual LayoutInflater // try return null; } finally { // Don't retain references on context. mConstructorArgs[0] = null; mConstructorArgs[1] = null; } } /** * android:onClick doesn't handle views with a ContextWrapper context. This method * backports new framework functionality to traverse the Context wrappers to find a * suitable target. */ private void checkOnClickListener(View view, AttributeSet attrs) { final Context context = view.getContext(); if (!(context instanceof ContextWrapper) || (Build.VERSION.SDK_INT >= 15 && !ViewCompat.hasOnClickListeners(view))) { // Skip our compat functionality if: the Context isn't a ContextWrapper, or // the view doesn't have an OnClickListener (we can only rely on this on API 15+ so // always use our compat code on older devices) return; } final TypedArray a = context.obtainStyledAttributes(attrs, sOnClickAttrs); final String handlerName = a.getString(0); if (handlerName != null) { view.setOnClickListener(new DeclaredOnClickListener(view, handlerName)); } a.recycle(); } private View createView(Context context, String name, String prefix) throws ClassNotFoundException, InflateException { Constructor<? extends View> constructor = sConstructorMap.get(name); try { if (constructor == null) { // Class not found in the cache, see if it's real, and try to add it Class<? extends View> clazz = context.getClassLoader() .loadClass(prefix != null ? (prefix + name) : name).asSubclass(View.class); constructor = clazz.getConstructor(sConstructorSignature); sConstructorMap.put(name, constructor); } constructor.setAccessible(true); return constructor.newInstance(mConstructorArgs); } catch (Exception e) { // We do not want to catch these, lets return null and let the actual LayoutInflater // try return null; } } /** * Allows us to emulate the {@code android:theme} attribute for devices before L. */ private static Context themifyContext(Context context, AttributeSet attrs, boolean useAndroidTheme, boolean useAppTheme) { final TypedArray a = context.obtainStyledAttributes(attrs, R.styleable.View, 0, 0); int themeId = 0; if (useAndroidTheme) { // First try reading android:theme if enabled themeId = a.getResourceId(R.styleable.View_android_theme, 0); } if (useAppTheme && themeId == 0) { // ...if that didn't work, try reading app:theme (for legacy reasons) if enabled themeId = a.getResourceId(R.styleable.View_theme, 0); if (themeId != 0) { Log.i(LOG_TAG, "app:theme is now deprecated. " + "Please move to using android:theme instead."); } } a.recycle(); if (themeId != 0 && (!(context instanceof ContextThemeWrapper) || ((ContextThemeWrapper) context).getThemeResId() != themeId)) { // If the context isn't a ContextThemeWrapper, or it is but does not have // the same theme as we need, wrap it in a new wrapper context = new ContextThemeWrapper(context, themeId); } return context; } /** * An implementation of OnClickListener that attempts to lazily load a * named click handling method from a parent or ancestor context. */ private static class DeclaredOnClickListener implements View.OnClickListener { private final View mHostView; private final String mMethodName; private Method mResolvedMethod; private Context mResolvedContext; public DeclaredOnClickListener(@NonNull View hostView, @NonNull String methodName) { mHostView = hostView; mMethodName = methodName; } @Override public void onClick(@NonNull View v) { if (mResolvedMethod == null) { resolveMethod(mHostView.getContext(), mMethodName); } try { mResolvedMethod.invoke(mResolvedContext, v); } catch (IllegalAccessException e) { throw new IllegalStateException("Could not execute non-public method for android:onClick", e); } catch (InvocationTargetException e) { throw new IllegalStateException("Could not execute method for android:onClick", e); } } @NonNull private void resolveMethod(@Nullable Context context, @NonNull String name) { while (context != null) { try { if (!context.isRestricted()) { final Method method = context.getClass().getMethod(mMethodName, View.class); if (method != null) { mResolvedMethod = method; mResolvedContext = context; return; } } } catch (NoSuchMethodException e) { // Failed to find method, keep searching up the hierarchy. } if (context instanceof ContextWrapper) { context = ((ContextWrapper) context).getBaseContext(); } else { // Can't search up the hierarchy, null out and fail. context = null; } } final int id = mHostView.getId(); final String idText = id == View.NO_ID ? "" : " with id '" + mHostView.getContext().getResources().getResourceEntryName(id) + "'"; throw new IllegalStateException("Could not find method " + mMethodName + "(View) in a parent or ancestor Context for android:onClick " + "attribute defined on view " + mHostView.getClass() + idText); } } }