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 17package android.widget; 18 19import android.content.Context; 20import android.util.AttributeSet; 21import android.view.MotionEvent; 22import android.view.PointerIcon; 23import android.widget.RemoteViews.RemoteView; 24 25 26/** 27 * A user interface element the user can tap or click to perform an action. 28 * 29 * <p>To display a button in an activity, add a button to the activity's layout XML file:</p> 30 * 31 * <pre> 32 * <Button 33 * android:id="@+id/button_id" 34 * android:layout_height="wrap_content" 35 * android:layout_width="wrap_content" 36 * android:text="@string/self_destruct" /></pre> 37 * 38 * <p>To specify an action when the button is pressed, set a click 39 * listener on the button object in the corresponding activity code:</p> 40 * 41 * <pre> 42 * public class MyActivity extends Activity { 43 * protected void onCreate(Bundle savedInstanceState) { 44 * super.onCreate(savedInstanceState); 45 * 46 * setContentView(R.layout.content_layout_id); 47 * 48 * final Button button = findViewById(R.id.button_id); 49 * button.setOnClickListener(new View.OnClickListener() { 50 * public void onClick(View v) { 51 * // Code here executes on main thread after user presses button 52 * } 53 * }); 54 * } 55 * }</pre> 56 * 57 * <p>The above snippet creates an instance of {@link View.OnClickListener} and wires 58 * the listener to the button using 59 * {@link #setOnClickListener setOnClickListener(View.OnClickListener)}. 60 * As a result, the system executes the code you write in {@code onClick(View)} after the 61 * user presses the button.</p> 62 * 63 * <p class="note">The system executes the code in {@code onClick} on the 64 * <a href="{@docRoot}guide/components/processes-and-threads.html#Threads">main thread</a>. 65 * This means your onClick code must execute quickly to avoid delaying your app's response 66 * to further user actions. See 67 * <a href="{@docRoot}training/articles/perf-anr.html">Keeping Your App Responsive</a> 68 * for more details.</p> 69 * 70 * <p>Every button is styled using the system's default button background, which is often 71 * different from one version of the platform to another. If you are not satisfied with the 72 * default button style, you can customize it. For more details and code samples, see the 73 * <a href="{@docRoot}guide/topics/ui/controls/button.html#Style">Styling Your Button</a> 74 * guide.</p> 75 * 76 * <p>For all XML style attributes available on Button see 77 * {@link android.R.styleable#Button Button Attributes}, 78 * {@link android.R.styleable#TextView TextView Attributes}, 79 * {@link android.R.styleable#View View Attributes}. See the 80 * {@link <a href="{@docRoot}guide/topics/ui/themes.html#ApplyingStyles">Styles and Themes</a> 81 * guide to learn how to implement and organize overrides to style-related attributes.</p> 82 * 83 * @see 84 * <a href="{@docRoot}guide/topics/ui/controls/button.html">Buttons Guide</a> 85 * {@link android.R.styleable#Button Styleable Button Attributes}, 86 * {@link android.R.styleable#TextView Styleable TextView Attributes}, 87 * {@link android.R.styleable#View Styleable View Attributes}, 88 * 89 */ 90@RemoteView 91public class Button extends TextView { 92 93 /** 94 * Simple constructor to use when creating a button from code. 95 * 96 * @param context The Context the Button is running in, through which it can 97 * access the current theme, resources, etc. 98 * 99 * @see #Button(Context, AttributeSet) 100 */ 101 public Button(Context context) { 102 this(context, null); 103 } 104 105 /** 106 * {@link LayoutInflater} calls this constructor when inflating a Button from XML. 107 * The attributes defined by the current theme's 108 * {@link android.R.attr#buttonStyle android:buttonStyle} 109 * override base view attributes. 110 * 111 * You typically do not call this constructor to create your own button instance in code. 112 * However, you must override this constructor when 113 * <a href="{@docRoot}training/custom-views/index.html">creating custom views</a>. 114 * 115 * @param context The Context the view is running in, through which it can 116 * access the current theme, resources, etc. 117 * @param attrs The attributes of the XML Button tag being used to inflate the view. 118 * 119 * @see #Button(Context, AttributeSet, int) 120 * @see android.view.View#View(Context, AttributeSet) 121 */ 122 public Button(Context context, AttributeSet attrs) { 123 this(context, attrs, com.android.internal.R.attr.buttonStyle); 124 } 125 126 /** 127 * This constructor allows a Button subclass to use its own class-specific base style from a 128 * theme attribute when inflating. The attributes defined by the current theme's 129 * {@code defStyleAttr} override base view attributes. 130 * 131 * <p>For Button's base view attributes see 132 * {@link android.R.styleable#Button Button Attributes}, 133 * {@link android.R.styleable#TextView TextView Attributes}, 134 * {@link android.R.styleable#View View Attributes}. 135 * 136 * @param context The Context the Button is running in, through which it can 137 * access the current theme, resources, etc. 138 * @param attrs The attributes of the XML Button tag that is inflating the view. 139 * @param defStyleAttr The resource identifier of an attribute in the current theme 140 * whose value is the the resource id of a style. The specified style’s 141 * attribute values serve as default values for the button. Set this parameter 142 * to 0 to avoid use of default values. 143 * @see #Button(Context, AttributeSet, int, int) 144 * @see android.view.View#View(Context, AttributeSet, int) 145 */ 146 public Button(Context context, AttributeSet attrs, int defStyleAttr) { 147 this(context, attrs, defStyleAttr, 0); 148 } 149 150 /** 151 * This constructor allows a Button subclass to use its own class-specific base style from 152 * either a theme attribute or style resource when inflating. To see how the final value of a 153 * particular attribute is resolved based on your inputs to this constructor, see 154 * {@link android.view.View#View(Context, AttributeSet, int, int)}. 155 * 156 * @param context The Context the Button is running in, through which it can 157 * access the current theme, resources, etc. 158 * @param attrs The attributes of the XML Button tag that is inflating the view. 159 * @param defStyleAttr The resource identifier of an attribute in the current theme 160 * whose value is the the resource id of a style. The specified style’s 161 * attribute values serve as default values for the button. Set this parameter 162 * to 0 to avoid use of default values. 163 * @param defStyleRes The identifier of a style resource that 164 * supplies default values for the button, used only if 165 * defStyleAttr is 0 or cannot be found in the theme. 166 * Set this parameter to 0 to avoid use of default values. 167 * 168 * @see #Button(Context, AttributeSet, int) 169 * @see android.view.View#View(Context, AttributeSet, int, int) 170 */ 171 public Button(Context context, AttributeSet attrs, int defStyleAttr, int defStyleRes) { 172 super(context, attrs, defStyleAttr, defStyleRes); 173 } 174 175 @Override 176 public CharSequence getAccessibilityClassName() { 177 return Button.class.getName(); 178 } 179 180 @Override 181 public PointerIcon onResolvePointerIcon(MotionEvent event, int pointerIndex) { 182 if (getPointerIcon() == null && isClickable() && isEnabled()) { 183 return PointerIcon.getSystemIcon(getContext(), PointerIcon.TYPE_HAND); 184 } 185 return super.onResolvePointerIcon(event, pointerIndex); 186 } 187} 188