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关于Activity的少许细节
1. 对活动应用样式和主题
2. 隐藏活动标题
3. 显示对话框窗口
4. 显示进度对话框
1. 应用样式和主题
改成
android:theme="@android:style/Theme.Dialog"
效果如下:
2. 隐藏活动的标题
比方说手机QQ登陆的时候,就会有一个全屏的QQ画面;说着微博也是,有一个全屏广告
protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); requestWindowFeature(Window.FEATURE_NO_TITLE); //隐藏标题 setContentView(R.layout.activity_main); Log.i(Tag, "onCreat()"); }
标题没有了:(我应该在这里放一幅画)
3.显示对话框窗口
(主要思想:重写Activity类中的onCreateDialog()方法)
(这里还谈到了“回调方法”目前先放一放)
现在布局文件里面加入一个button,然后在activity中绑定事件,然后在onClick()中填入代码
<Button android:id="@+id/btn1" android:layout_width="match_parent" android:layout_height="wrap_content" android:text="显示对话框" />
public class MainActivity extends Activity implements OnClickListener{ private Button btn; CharSequence[] items = {"你","我","他"}; boolean[] checkedItems = new boolean[items.length]; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); btn = (Button) findViewById(R.id.btn1); btn.setOnClickListener(this); } @Override public void onClick(View v) { showDialog(0); //坑爹啊,这方法过时了? } @Override @Deprecated protected Dialog onCreateDialog(int id) { //下面填代码 switch (id) { case 0: return new AlertDialog.Builder(this) .setIcon(R.drawable.ic_launcher) .setTitle("这是个简单的对话框..") .setPositiveButton("OK", new DialogInterface.OnClickListener() { @Override public void onClick(DialogInterface dialog, int which) { Toast.makeText(getBaseContext(), "OK被点击了", Toast.LENGTH_LONG).show(); //Toast是一种提示框,Toast.LENGTH_LONG表示它显示时间长 } }) .setNegativeButton("Cancel",new DialogInterface.OnClickListener() { @Override public void onClick(DialogInterface dialog, int which) { Toast.makeText(getBaseContext(), "Cancel被点击了", Toast.LENGTH_LONG).show(); //Toast是一种提示框,Toast.LENGTH_LONG表示它显示时间长 } }) .setMultiChoiceItems(items, checkedItems, new DialogInterface.OnMultiChoiceClickListener() { @Override public void onClick(DialogInterface dialog, int which, boolean isChecked) { Toast.makeText(getBaseContext(), items[which]+(isChecked?"Checked!":"unCkecked!"), Toast.LENGTH_LONG).show(); } }) .create(); case 1: break; default: break; } return null; }}
大概玩明白咋回事儿了。
showDialog()一旦被执行,它就去调用onCreateDialog()这个由Activity管理的方法。------回调
补充:
Toast android.widget.Toast.makeText(Context context, CharSequence text, int duration)
Make a standard toast that just contains a text view.
- Parameters:
- context The context to use. Usually your
android.app.Application
orandroid.app.Activity
object.- text The text to show. Can be formatted text.
- duration How long to display the message. Either
LENGTH_SHORT
orLENGTH_LONG
- text The text to show. Can be formatted text.
实际上,再看上面的代码,
setPositiveButton(String text,new DialogInterface.OnClickListener(){}) 这方法设置了一个OK按钮
setNegativeButton(String text,new DialogInterface.OnClickListener(){}) 这方法设置了一个Cancel按钮
setMultiChoiceItems(CharSequence[] items, boolean[] checkedItems,new DialogInterface.OnMultiChoiceClickListener()) 设置了一个复选框列表
而且代码一开始的
new AlertDialog.Builder(this)
实际上返回 Builder对象,完全可以写成:
Builder builder = new AlertDialog.Builder(this);
然后就是跟上面代码差不多:
builder.setPositiveButton();
builder.setNegativeButton();
….
switch代码块里面返回 builder.create()就好了
程序中多次用到Context类以及其引用,实际上,Activity是Context的子类
如果在activity中引用context对象,那么可以在外部成员变量的地方声明一个 :
private Context context = this;
之后就不用总是getBaseContext(); 而直接用context就好了。
但是上面的Toast.makeText(getBaseContext(),”ok clicked”,Toast.LENGTH_LONG)由于toast在AlertDialog中使用,所以还是应该用getBaseContext()
4. 显示进度对话框
基本上就是尝试着用代码开一个线程去做后台的事儿---假装我们在做什么,前台呢?显示模态进度条对话框,由于是模态(操作系统术语)所以阻塞了用户界面。
public class MainActivity extends Activity implements OnClickListener{ private Button btn; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); btn = (Button) findViewById(R.id.btn1); btn.setOnClickListener(this); } @Override public void onClick(View v) { final ProgressDialog dialog = ProgressDialog.show(this,"我们在处理中", "拼命加载中",true); new Thread(new Runnable() { @Override public void run() {// try // {// Thread.sleep(5000); //假装我们在做什么// //好,我们已经做完了,等够5秒了// dialog.dismiss();// } // catch (Exception e) // {// e.printStackTrace();// } SystemClock.sleep(5000);//假装我们在做什么,这样写不用try catch dialog.dismiss(); } }).start(); }}
然后5秒,这进度条就不见了.
dialog.dismiss()了
既然要假装做点儿什么,来做点儿实际的:
修改MainActivity .java
public class MainActivity extends Activity implements OnClickListener{ private Button btn; private ProgressDialog progressDialog; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); btn = (Button) findViewById(R.id.btn1); btn.setOnClickListener(this); } @Override public void onClick(View v) { showDialog(0); progressDialog.setProgress(0); new Thread(new Runnable() { @Override public void run() { for (int i = 0; i < 15; i++) { SystemClock.sleep(5000); int temp = (int)(100/15); progressDialog.incrementProgressBy(temp);//更新进度条 } progressDialog.dismiss(); } }).start(); } @Override @Deprecated protected Dialog onCreateDialog(int id) { switch (id) { case 0: progressDialog = new ProgressDialog(this); //return progressDialog.setIcon(R.drawable.ic_launcher); progressDialog.setTitle((CharSequence)"正在拼命加载中..."); progressDialog.setProgressStyle(ProgressDialog.STYLE_HORIZONTAL); progressDialog.setButton(DialogInterface.BUTTON_POSITIVE,"ok", new DialogInterface.OnClickListener() { @Override public void onClick(DialogInterface dialog, int which) { Toast.makeText(getBaseContext(), "ok clicked", Toast.LENGTH_LONG).show(); } }); progressDialog.setButton(DialogInterface.BUTTON_NEGATIVE,"cancel", new DialogInterface.OnClickListener() { @Override public void onClick(DialogInterface dialog, int which) { Toast.makeText(getBaseContext(), "cancel clicked", Toast.LENGTH_LONG).show(); } }); return progressDialog; default: break; } return null; }}
在activity中显示dialog,这里一样用的showDialog(),然后重写onCreateDialog() 方法
onCreateDialog()里面显示一个进度条对话框,然后新线程就负责动态更新它。
progressDialog.dismiss()方法关闭该对话框。
关于Activity的少许细节