—— 不管前方的路有多苦，只要走的方向正确，不管多么崎岖不平，都比站在原地接近幸福。——宫崎骏
上一篇我们讲了进度条控件ProgressBar的基本用法，这里来学习对话框AlertDialog的基本用法。
AlertDialog是什么
AlertDialog是一个Android自带的提示对话框。
AlertDialog有什么用
AlertDialog一般用来显示比较简单的提示对话框，比如只有标题、内容、几个按钮的对话框。
AlertDialog怎么用
继续基于上一篇的项目，我们增加几个对话框AlertDialog：
| 123456789101112131415161718192021222324252627282930313233343536373839404142434445464748495051525354 | <?``xml version``=``"1.0" encoding``=``"utf-8"``?>``<``androidx.constraintlayout.widget.ConstraintLayout xmlns:android``=``"http://schemas.android.com/apk/res/android"`` ``xmlns:app``=``"http://schemas.android.com/apk/res-auto"`` ``xmlns:tools``=``"http://schemas.android.com/tools"`` ``android:layout_width``=``"match_parent"`` ``android:layout_height``=``"match_parent"`` ``tools:context``=``".TestActivity"``>`` ``<``ScrollView`` ``android:layout_width``=``"match_parent"`` ``android:layout_height``=``"wrap_content"`` ``app:layout_constraintBottom_toBottomOf``=``"parent"`` ``app:layout_constraintTop_toTopOf``=``"parent"`` ``app:layout_constraintVertical_bias``=``"0.0"``>`` ``...`` ``...`` ``...`` ``<``LinearLayout`` ``android:id``=``"@+id/layout1"`` ``android:layout_width``=``"match_parent"`` ``android:layout_height``=``"wrap_content"`` ``app:layout_constraintStart_toStartOf``=``"@+id/progress_horizontal3"`` ``app:layout_constraintTop_toBottomOf``=``"@+id/progress_horizontal3"``>`` ``<``Button`` ``android:id``=``"@+id/btn1"`` ``android:layout_width``=``"wrap_content"`` ``android:layout_height``=``"wrap_content"`` ``android:text``=``"对话框1" />`` ``<``Button`` ``android:id``=``"@+id/btn2"`` ``android:layout_width``=``"wrap_content"`` ``android:layout_height``=``"wrap_content"`` ``android:text``=``"对话框2" />`` ``<``Button`` ``android:id``=``"@+id/btn3"`` ``android:layout_width``=``"wrap_content"`` ``android:layout_height``=``"wrap_content"`` ``android:text``=``"对话框3" />`` ``<``Button`` ``android:id``=``"@+id/btn4"`` ``android:layout_width``=``"wrap_content"`` ``android:layout_height``=``"wrap_content"`` ``android:text``=``"对话框4" />`` ``</``LinearLayout``>`` ``</``androidx.constraintlayout.widget.ConstraintLayout``>`` ``</``ScrollView``>``</``androidx.constraintlayout.widget.ConstraintLayout``> |
|---|
上面加了四个按钮，点击每个分别会弹出对话框，我们看点击第一个按钮弹出来的对话框，这种对话框的特点是显示的信息非常简单，标题+内容+1-3个按钮，标题设置了就显示，没设置就不显示，按钮也是一样，如下：
对应的对话框代码：
| 123456789101112131415 | new AlertDialog.Builder(TestActivity.``this``)`` ``.setTitle(``"系统提示"``)`` ``.setMessage(``"确定删除？"``)`` ``.setNegativeButton(``"取消"``, ``new DialogInterface.OnClickListener() {`` ``@Override`` ``public void onClick(DialogInterface dialog, ``int which) {`` ``Toast.makeText(TestActivity.``this``, ``"点击了取消"``, Toast.LENGTH_SHORT).show();`` ``}`` ``})`` ``.setPositiveButton(``"确定"``, ``new DialogInterface.OnClickListener() {`` ``@Override`` ``public void onClick(DialogInterface dialog, ``int which) {`` ``Toast.makeText(TestActivity.``this``, ``"点击了确定"``, Toast.LENGTH_SHORT).show();`` ``}`` ``}).show(); |
|---|
第二种对话框，特点是标题+非常简单的列表样式对话框，标题设置了就显示，没设置就不显示，只限如下图这种纯简单文字的列表：
对应的对话框代码：
| 123456789 | new AlertDialog.Builder(TestActivity.``this``)`` ``.setTitle(``"要发送给"``)`` ``.setItems(str, ``new DialogInterface.OnClickListener() {`` ``@Override`` ``public void onClick(DialogInterface dialog, ``int which) {`` ``Toast.makeText(TestActivity.``this``, ``"点击了 " + str[which], Toast.LENGTH_SHORT).show();`` ``}`` ``})`` ``.show(); |
|---|
第三种对话框，标题+xml布局文件+1-3个按钮，标题设置了就显示，没设置就不显示，按钮也是一样，如图：
对应的对话框代码：
| 123456789101112131415 | new AlertDialog.Builder(TestActivity.``this``)`` ``.setTitle(``"Apple ID 登录"``)`` ``.setView(R.layout.dialog_my1)`` ``.setNegativeButton(``"取消"``, ``new DialogInterface.OnClickListener() {`` ``@Override`` ``public void onClick(DialogInterface dialog, ``int which) {`` ``Toast.makeText(TestActivity.``this``, ``"点击了取消"``, Toast.LENGTH_SHORT).show();`` ``}`` ``})`` ``.setPositiveButton(``"确定"``, ``new DialogInterface.OnClickListener() {`` ``@Override`` ``public void onClick(DialogInterface dialog, ``int which) {`` ``Toast.makeText(TestActivity.``this``, ``"点击了确定"``, Toast.LENGTH_SHORT).show();`` ``}`` ``}).show(); |
|---|
布局文件：
| 1234567891011121314151617181920212223242526272829303132 | <?``xml version``=``"1.0" encoding``=``"utf-8"``?>``<``androidx.constraintlayout.widget.ConstraintLayout xmlns:android``=``"http://schemas.android.com/apk/res/android"`` ``xmlns:app``=``"http://schemas.android.com/apk/res-auto"`` ``xmlns:tools``=``"http://schemas.android.com/tools"`` ``android:layout_width``=``"match_parent"`` ``android:layout_height``=``"match_parent"`` ``tools:context``=``".MainActivity"``>`` ``<``EditText`` ``android:id``=``"@+id/edittext1"`` ``android:layout_width``=``"match_parent"`` ``android:layout_height``=``"wrap_content"`` ``android:background``=``"@drawable/bg_rectangle_c8c8c8_2"`` ``android:hint``=``"请输入账号"`` ``android:padding``=``"10dp"`` ``app:layout_constraintEnd_toEndOf``=``"parent"`` ``app:layout_constraintStart_toStartOf``=``"parent"`` ``app:layout_constraintTop_toTopOf``=``"parent" />`` ``<``EditText`` ``android:id``=``"@+id/edittext2"`` ``android:layout_width``=``"match_parent"`` ``android:layout_height``=``"wrap_content"`` ``android:background``=``"@drawable/bg_rectangle_c8c8c8_2"`` ``android:hint``=``"请输入密码"`` ``android:inputType``=``"textPassword"`` ``android:padding``=``"10dp"`` ``app:layout_constraintEnd_toEndOf``=``"parent"`` ``app:layout_constraintStart_toStartOf``=``"parent"`` ``app:layout_constraintTop_toBottomOf``=``"@+id/edittext1" />``</``androidx.constraintlayout.widget.ConstraintLayout``> |
|---|
第四种对话框，也是我们最常用的自定义样式对话框，这种对话框从头到尾都是通过布局文件、style设置来自定义样式的，如图：
对应的对话框代码：
| 12345678910111213141516171819202122232425 | class MyDialog ``extends Dialog {`` ``public MyDialog(Context context) {`` ``super``(context, R.style.MyDialog);`` ``setContentView(R.layout.dialog_my2);`` ``getWindow().getAttributes().gravity = Gravity.CENTER;`` ``WindowManager.LayoutParams lp = getWindow().getAttributes();`` ``DisplayMetrics metrics = TestActivity.``this``.getResources().getDisplayMetrics();`` ``lp.width = (``int``) (metrics.widthPixels * ``0``.8f);`` ``getWindow().setAttributes(lp);`` ``findViewById(R.id.tv_left).setOnClickListener(``new View.OnClickListener() {`` ``@Override`` ``public void onClick(View v) {`` ``dismiss();`` ``}`` ``});`` ``findViewById(R.id.tv_right).setOnClickListener(``new View.OnClickListener() {`` ``@Override`` ``public void onClick(View v) {`` ``dismiss();`` ``}`` ``});`` ``}``} |
|---|
布局文件：
| 123456789101112131415161718192021222324252627282930313233343536373839404142434445464748495051525354555657585960616263646566676869707172737475767778798081828384858687888990919293949596 | <?``xml version``=``"1.0" encoding``=``"utf-8"``?>``<``androidx.constraintlayout.widget.ConstraintLayout xmlns:android``=``"http://schemas.android.com/apk/res/android"`` ``xmlns:app``=``"http://schemas.android.com/apk/res-auto"`` ``xmlns:tools``=``"http://schemas.android.com/tools"`` ``android:layout_width``=``"match_parent"`` ``android:layout_height``=``"wrap_content"`` ``android:background``=``"@drawable/bg_rectangle_white_12"`` ``tools:context``=``".MainActivity"``>`` ``<``TextView`` ``android:id``=``"@+id/tv_title"`` ``android:layout_width``=``"wrap_content"`` ``android:layout_height``=``"wrap_content"`` ``android:layout_marginTop``=``"20dp"`` ``android:text``=``"微信想访问您的照片"`` ``android:textColor``=``"#222222"`` ``android:textSize``=``"16sp"`` ``app:layout_constraintEnd_toEndOf``=``"parent"`` ``app:layout_constraintStart_toStartOf``=``"parent"`` ``app:layout_constraintTop_toTopOf``=``"parent" />`` ``<``TextView`` ``android:id``=``"@+id/tv_1"`` ``android:layout_width``=``"wrap_content"`` ``android:layout_height``=``"wrap_content"`` ``android:layout_marginTop``=``"6dp"`` ``android:text``=``"请点击好以允许访问。"`` ``android:textColor``=``"#666666"`` ``app:layout_constraintEnd_toEndOf``=``"parent"`` ``app:layout_constraintStart_toStartOf``=``"parent"`` ``app:layout_constraintTop_toBottomOf``=``"@+id/tv_title" />`` ``<``TextView`` ``android:id``=``"@+id/tv_2"`` ``android:layout_width``=``"match_parent"`` ``android:layout_height``=``"wrap_content"`` ``android:layout_marginLeft``=``"30dp"`` ``android:layout_marginTop``=``"14dp"`` ``android:layout_marginRight``=``"30dp"`` ``android:text``=``"若不允许，您将无法在微信中给好友发送照片、保存照片，也无法在朋友圈中发表照片。"`` ``android:textColor``=``"#666666"`` ``app:layout_constraintEnd_toEndOf``=``"parent"`` ``app:layout_constraintStart_toStartOf``=``"parent"`` ``app:layout_constraintTop_toBottomOf``=``"@+id/tv_1" />`` ``<``View`` ``android:id``=``"@+id/view1"`` ``android:layout_width``=``"match_parent"`` ``android:layout_height``=``"1px"`` ``android:layout_marginTop``=``"30dp"`` ``android:background``=``"#cccccc"`` ``app:layout_constraintEnd_toEndOf``=``"parent"`` ``app:layout_constraintStart_toStartOf``=``"parent"`` ``app:layout_constraintTop_toBottomOf``=``"@+id/tv_2" />`` ``<``LinearLayout`` ``android:layout_width``=``"match_parent"`` ``android:layout_height``=``"wrap_content"`` ``app:layout_constraintEnd_toEndOf``=``"parent"`` ``app:layout_constraintStart_toStartOf``=``"parent"`` ``app:layout_constraintTop_toBottomOf``=``"@+id/view1"``>`` ``<``TextView`` ``android:id``=``"@+id/tv_left"`` ``android:layout_width``=``"0dp"`` ``android:layout_height``=``"wrap_content"`` ``android:layout_weight``=``"1"`` ``android:gravity``=``"center"`` ``android:paddingTop``=``"10dp"`` ``android:paddingBottom``=``"10dp"`` ``android:text``=``"不允许"`` ``android:textColor``=``"#226fff"`` ``app:layout_constraintEnd_toEndOf``=``"parent"`` ``app:layout_constraintStart_toStartOf``=``"parent" />`` ``<``View`` ``android:layout_width``=``"1px"`` ``android:layout_height``=``"match_parent"`` ``android:background``=``"#cccccc" />`` ``<``TextView`` ``android:id``=``"@+id/tv_right"`` ``android:layout_width``=``"0dp"`` ``android:layout_height``=``"wrap_content"`` ``android:layout_weight``=``"1"`` ``android:gravity``=``"center"`` ``android:paddingTop``=``"10dp"`` ``android:paddingBottom``=``"10dp"`` ``android:text``=``"好"`` ``android:textColor``=``"#226fff"`` ``app:layout_constraintEnd_toEndOf``=``"parent"`` ``app:layout_constraintStart_toStartOf``=``"parent" />`` ``</``LinearLayout``>``</``androidx.constraintlayout.widget.ConstraintLayout``> |
|---|
