对话框
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对话框（Dialog）是一种常用的 UI 组件，它主要用于显示信息、接收用户操作反馈
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对话框可以包含各种元素，但是主要还是以文本、按钮为主，其次是列表
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其中，基础对话框是 Android 中最简单的对话框，而后是进度对话框、自定义对话框等
一、UI 线程问题
1、非 UI 线程中创建对话框
- 非 UI 线程中创建对话框会抛出异常
try {AlertDialog.Builder builder = new AlertDialog.Builder(this);builder.setTitle("普通对话框");builder.setMessage("确定退出吗？");builder.setPositiveButton("确定", (dialog, which) -> {Toast.makeText(this, "点击了确定", Toast.LENGTH_SHORT).show();});builder.setNegativeButton("取消", (dialog, which) -> {Toast.makeText(this, "点击了取消", Toast.LENGTH_SHORT).show();});AlertDialog alertDialog = builder.create();alertDialog.show();
} catch (Exception e) {e.printStackTrace();
}
- 输出结果
java.lang.RuntimeException: Can't create handler inside thread Thread[Thread-2,5,main] that has not called Looper.prepare()
2、非 UI 线程中显示对话框
- 非 UI 线程中显示对话框会抛出异常
AlertDialog.Builder builder = new AlertDialog.Builder(this);builder.setTitle("普通对话框");
builder.setMessage("确定退出吗？");
builder.setPositiveButton("确定", (dialog, which) -> {Toast.makeText(this, "点击了确定", Toast.LENGTH_SHORT).show();
});
builder.setNegativeButton("取消", (dialog, which) -> {Toast.makeText(this, "点击了取消", Toast.LENGTH_SHORT).show();
});AlertDialog alertDialog = builder.create();new Thread(() -> {try {alertDialog.show();} catch (Exception e) {e.printStackTrace();}
}).start();
- 输出结果
java.lang.RuntimeException: Can't create handler inside thread Thread[Thread-2,5,main] that has not called Looper.prepare()
3、非 UI 线程中关闭对话框
- 非 UI 线程中关闭对话框不会抛出异常
AlertDialog.Builder builder = new AlertDialog.Builder(this);builder.setTitle("普通对话框");
builder.setMessage("确定退出吗？");
builder.setPositiveButton("确定", (dialog, which) -> {Toast.makeText(this, "点击了确定", Toast.LENGTH_SHORT).show();
});
builder.setNegativeButton("取消", (dialog, which) -> {Toast.makeText(this, "点击了取消", Toast.LENGTH_SHORT).show();
});AlertDialog alertDialog = builder.create();alertDialog.show();new Thread(() -> {try {Thread.sleep(5 * 1000);alertDialog.dismiss();} catch (Exception e) {e.printStackTrace();}
}).start();
二、外部取消
1、普通对话框外部取消
- 通过
setCancelable(boolean cancelable)方法设置普通对话框是否可以通过点击外部区域来取消
AlertDialog.Builder builder = new AlertDialog.Builder(this);builder.setTitle("普通对话框");
builder.setMessage("确定退出吗？");
builder.setPositiveButton("确定", (dialog, which) -> {Toast.makeText(this, "点击了确定", Toast.LENGTH_SHORT).show();
});
builder.setNegativeButton("取消", (dialog, which) -> {Toast.makeText(this, "点击了取消", Toast.LENGTH_SHORT).show();
});builder.setCancelable(false); // 不建议使用AlertDialog alertDialog = builder.create();alertDialog.show();
2、单选对话框外部取消
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通过
setCancelable(boolean cancelable)方法设置单选对话框是否可以通过点击外部区域来取消 -
但是不建议对单选对话框禁止点击外部区域来取消，因为用户可能误触发了单选对话框，本来不想做选择
AlertDialog.Builder builder = new AlertDialog.Builder(this);builder.setTitle("单选对话框");String[] items = {"物理", "化学", "生物", "历史"};
builder.setSingleChoiceItems(items, -1, (dialog, which) -> {Toast.makeText(this, "选择了：" + items[which], Toast.LENGTH_SHORT).show();dialog.dismiss();
});builder.setCancelable(false); // 不建议使用AlertDialog alertDialog = builder.create();alertDialog.show();
3、多选对话框外部取消
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通过
setCancelable(boolean cancelable)方法设置多选对话框是否可以通过点击外部区域来取消 -
但是不建议对多选对话框禁止点击外部区域来取消，因为用户可能误触发了多选对话框，本来不想做选择
AlertDialog.Builder builder = new AlertDialog.Builder(this);builder.setTitle("多选对话框");String[] items = {"胡萝卜", "白菜", "菠菜", "土豆", "黄瓜", "西红柿"};
boolean[] check = {false, false, false, false, false, false};
builder.setMultiChoiceItems(items, check, (dialog, which, isChecked) -> {if (isChecked) {check[which] = true;Toast.makeText(this, "你选中了：" + items[which], Toast.LENGTH_SHORT).show();} else {check[which] = false;Toast.makeText(this, "你取消了：" + items[which], Toast.LENGTH_SHORT).show();}
});builder.setCancelable(false); // 不建议使用AlertDialog alertDialog = builder.create();alertDialog.show();
4、列表对话框外部取消
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通过
setCancelable(boolean cancelable)方法设置列表对话框是否可以通过点击外部区域来取消 -
但是不建议对列表对话框禁止点击外部区域来取消，因为用户可能误触发了列表对话框，本来不想做选择
AlertDialog.Builder builder = new AlertDialog.Builder(this);builder.setTitle("课程安排：");String[] items = {"第一节（数学）", "第二节（地理）", "第三节（历史）", "第四节（美术）"};
builder.setItems(items, (dialog, which) -> {Toast.makeText(this, items[which], Toast.LENGTH_SHORT).show();
});builder.setCancelable(false);AlertDialog alertDialog = builder.create();alertDialog.show();
三、冲突问题
1、单选对话框冲突问题
- setSingleChoiceItems 方法与 setMessage 方法显示区域互相冲突，同时使用时，setMessage 方法设置的内容会覆盖掉 setSingleChoiceItems 方法设置的内容
AlertDialog.Builder builder = new AlertDialog.Builder(this);builder.setTitle("单选对话框");
builder.setMessage("这是单选对话框");
String[] items = {"物理", "化学", "生物", "历史"};
builder.setSingleChoiceItems(items, -1, (dialog, which) -> {Toast.makeText(this, "选择了：" + items[which], Toast.LENGTH_SHORT).show();dialog.dismiss();
});AlertDialog alertDialog = builder.create();alertDialog.show();
2、多选对话框冲突问题
- setMultiChoiceItems 方法与 setMessage 方法显示区域互相冲突，同时使用时，setMessage 方法设置的内容会覆盖掉 setMultiChoiceItems 方法设置的内容
AlertDialog.Builder builder = new AlertDialog.Builder(this);builder.setTitle("多选对话框");
builder.setMessage("这是多选对话框");
String[] items = {"胡萝卜", "白菜", "菠菜", "土豆", "黄瓜", "西红柿"};
boolean[] check = {false, false, false, false, false, false};
builder.setMultiChoiceItems(items, check, (dialog, which, isChecked) -> {if (isChecked) {check[which] = true;Toast.makeText(this, "你选中了：" + items[which], Toast.LENGTH_SHORT).show();} else {check[which] = false;Toast.makeText(this, "你取消了：" + items[which], Toast.LENGTH_SHORT).show();}
});AlertDialog alertDialog = builder.create();alertDialog.show();
3、列表对话框冲突问题
- setItems 方法与 setMessage 方法显示区域互相冲突，同时使用时，setMessage 方法设置的内容会覆盖掉 setItems 方法设置的内容
AlertDialog.Builder builder = new AlertDialog.Builder(this);builder.setTitle("课程安排：");
builder.setMessage("这是列表对话框");
String[] items = {"第一节（数学）", "第二节（地理）", "第三节（历史）", "第四节（美术）"};
builder.setItems(items, (dialog, which) -> {Toast.makeText(this, items[which], Toast.LENGTH_SHORT).show();
});builder.setCancelable(false);AlertDialog alertDialog = builder.create();alertDialog.show();
四、dismiss 方法与 hide 方法
1、基本介绍
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dismiss 方法：用于完全关闭并移除 AlertDialog，一旦调用此方法，AlertDialog 将不再显示在屏幕上，且相关的资源会被移除
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hide 方法：用于关闭 AlertDialog，一旦调用此方法，AlertDialog 将不再显示在屏幕上，但相关的资源不会被移除
2、演示
AlertDialog.Builder builder = new AlertDialog.Builder(this);builder.setTitle("普通对话框");
builder.setMessage("确定退出吗？");
builder.setPositiveButton("确定", (dialog, which) -> {Toast.makeText(this, "点击了确定", Toast.LENGTH_SHORT).show();
});
builder.setNegativeButton("取消", (dialog, which) -> {Toast.makeText(this, "点击了取消", Toast.LENGTH_SHORT).show();
});AlertDialog alertDialog = builder.create();alertDialog.show();Handler handler = new Handler();handler.postDelayed(() -> alertDialog.hide(), 5 * 1000);