1 /* 2 * Copyright (C) 2006 The Android Open Source Project 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); 5 * you may not use this file except in compliance with the License. 6 * You may obtain a copy of the License at 7 * 8 * http://www.apache.org/licenses/LICENSE-2.0 9 * 10 * Unless required by applicable law or agreed to in writing, software 11 * distributed under the License is distributed on an "AS IS" BASIS, 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 * See the License for the specific language governing permissions and 14 * limitations under the License. 15 */ 16 17 package android.widget; 18 19 import android.content.Context; 20 import android.util.AttributeSet; 21 import android.view.LayoutInflater; 22 import android.view.MotionEvent; 23 import android.view.PointerIcon; 24 import android.widget.RemoteViews.RemoteView; 25 26 27 /** 28 * A user interface element the user can tap or click to perform an action. 29 * 30 * <p>To display a button in an activity, add a button to the activity's layout XML file:</p> 31 * 32 * <pre> 33 * <Button 34 * android:id="@+id/button_id" 35 * android:layout_height="wrap_content" 36 * android:layout_width="wrap_content" 37 * android:text="@string/self_destruct" /></pre> 38 * 39 * <p>To specify an action when the button is pressed, set a click 40 * listener on the button object in the corresponding activity code:</p> 41 * 42 * <pre> 43 * public class MyActivity extends Activity { 44 * protected void onCreate(Bundle savedInstanceState) { 45 * super.onCreate(savedInstanceState); 46 * 47 * setContentView(R.layout.content_layout_id); 48 * 49 * final Button button = findViewById(R.id.button_id); 50 * button.setOnClickListener(new View.OnClickListener() { 51 * public void onClick(View v) { 52 * // Code here executes on main thread after user presses button 53 * } 54 * }); 55 * } 56 * }</pre> 57 * 58 * <p>The above snippet creates an instance of {@link android.view.View.OnClickListener} and wires 59 * the listener to the button using 60 * {@link #setOnClickListener setOnClickListener(View.OnClickListener)}. 61 * As a result, the system executes the code you write in {@code onClick(View)} after the 62 * user presses the button.</p> 63 * 64 * <p class="note">The system executes the code in {@code onClick} on the 65 * <a href="{@docRoot}guide/components/processes-and-threads.html#Threads">main thread</a>. 66 * This means your onClick code must execute quickly to avoid delaying your app's response 67 * to further user actions. See 68 * <a href="{@docRoot}training/articles/perf-anr.html">Keeping Your App Responsive</a> 69 * for more details.</p> 70 * 71 * <p>Every button is styled using the system's default button background, which is often 72 * different from one version of the platform to another. If you are not satisfied with the 73 * default button style, you can customize it. For more details and code samples, see the 74 * <a href="{@docRoot}guide/topics/ui/controls/button.html#Style">Styling Your Button</a> 75 * guide.</p> 76 * 77 * <p>For all XML style attributes available on Button see 78 * {@link android.R.styleable#Button Button Attributes}, 79 * {@link android.R.styleable#TextView TextView Attributes}, 80 * {@link android.R.styleable#View View Attributes}. See the 81 * <a href="{@docRoot}guide/topics/ui/themes.html#ApplyingStyles">Styles and Themes</a> 82 * guide to learn how to implement and organize overrides to style-related attributes.</p> 83 */ 84 @RemoteView 85 public class Button extends TextView { 86 87 /** 88 * Simple constructor to use when creating a button from code. 89 * 90 * @param context The Context the Button is running in, through which it can 91 * access the current theme, resources, etc. 92 * 93 * @see #Button(Context, AttributeSet) 94 */ Button(Context context)95 public Button(Context context) { 96 this(context, null); 97 } 98 99 /** 100 * {@link LayoutInflater} calls this constructor when inflating a Button from XML. 101 * The attributes defined by the current theme's 102 * {@link android.R.attr#buttonStyle android:buttonStyle} 103 * override base view attributes. 104 * 105 * You typically do not call this constructor to create your own button instance in code. 106 * However, you must override this constructor when 107 * <a href="{@docRoot}training/custom-views/index.html">creating custom views</a>. 108 * 109 * @param context The Context the view is running in, through which it can 110 * access the current theme, resources, etc. 111 * @param attrs The attributes of the XML Button tag being used to inflate the view. 112 * 113 * @see #Button(Context, AttributeSet, int) 114 * @see android.view.View#View(Context, AttributeSet) 115 */ Button(Context context, AttributeSet attrs)116 public Button(Context context, AttributeSet attrs) { 117 this(context, attrs, com.android.internal.R.attr.buttonStyle); 118 } 119 120 /** 121 * This constructor allows a Button subclass to use its own class-specific base style from a 122 * theme attribute when inflating. The attributes defined by the current theme's 123 * {@code defStyleAttr} override base view attributes. 124 * 125 * <p>For Button's base view attributes see 126 * {@link android.R.styleable#Button Button Attributes}, 127 * {@link android.R.styleable#TextView TextView Attributes}, 128 * {@link android.R.styleable#View View Attributes}. 129 * 130 * @param context The Context the Button is running in, through which it can 131 * access the current theme, resources, etc. 132 * @param attrs The attributes of the XML Button tag that is inflating the view. 133 * @param defStyleAttr The resource identifier of an attribute in the current theme 134 * whose value is the the resource id of a style. The specified style’s 135 * attribute values serve as default values for the button. Set this parameter 136 * to 0 to avoid use of default values. 137 * @see #Button(Context, AttributeSet, int, int) 138 * @see android.view.View#View(Context, AttributeSet, int) 139 */ Button(Context context, AttributeSet attrs, int defStyleAttr)140 public Button(Context context, AttributeSet attrs, int defStyleAttr) { 141 this(context, attrs, defStyleAttr, 0); 142 } 143 144 /** 145 * This constructor allows a Button subclass to use its own class-specific base style from 146 * either a theme attribute or style resource when inflating. To see how the final value of a 147 * particular attribute is resolved based on your inputs to this constructor, see 148 * {@link android.view.View#View(Context, AttributeSet, int, int)}. 149 * 150 * @param context The Context the Button is running in, through which it can 151 * access the current theme, resources, etc. 152 * @param attrs The attributes of the XML Button tag that is inflating the view. 153 * @param defStyleAttr The resource identifier of an attribute in the current theme 154 * whose value is the the resource id of a style. The specified style’s 155 * attribute values serve as default values for the button. Set this parameter 156 * to 0 to avoid use of default values. 157 * @param defStyleRes The identifier of a style resource that 158 * supplies default values for the button, used only if 159 * defStyleAttr is 0 or cannot be found in the theme. 160 * Set this parameter to 0 to avoid use of default values. 161 * 162 * @see #Button(Context, AttributeSet, int) 163 * @see android.view.View#View(Context, AttributeSet, int, int) 164 */ Button(Context context, AttributeSet attrs, int defStyleAttr, int defStyleRes)165 public Button(Context context, AttributeSet attrs, int defStyleAttr, int defStyleRes) { 166 super(context, attrs, defStyleAttr, defStyleRes); 167 } 168 169 @Override getAccessibilityClassName()170 public CharSequence getAccessibilityClassName() { 171 return Button.class.getName(); 172 } 173 174 @Override onResolvePointerIcon(MotionEvent event, int pointerIndex)175 public PointerIcon onResolvePointerIcon(MotionEvent event, int pointerIndex) { 176 if (getPointerIcon() == null && isClickable() && isEnabled()) { 177 return PointerIcon.getSystemIcon(getContext(), PointerIcon.TYPE_HAND); 178 } 179 return super.onResolvePointerIcon(event, pointerIndex); 180 } 181 } 182