Android Menu(Context Menu,Options Menu,SubMenu)实例
16lz
2021-01-23
package com.cocol.activity;import android.app.Activity;import android.os.Bundle;import android.util.Log;import android.view.ContextMenu;import android.view.ContextMenu.ContextMenuInfo;import android.view.Menu;import android.view.MenuItem;import android.view.SubMenu;import android.view.View;import android.widget.TextView;import android.widget.Toast;public class MenuActivity extends Activity{ private final int MENU_ADD=1,MENU_SEND=2,MENU_DEL=3; private final int GROUP_DEFAULT=0,GROUP_DEL=1; private final int ID_DEFAULT=0; private final int ID_TEXT1=1,ID_TEXT2=2,ID_TEXT3=3; private String[] choices={"Press Me","Try Again","Change Me"}; private static int itemNum=0; private static TextView bv; @Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.menu_layout);bv=(TextView)findViewById(R.id.focus_text);this.registerForContextMenu(bv);}@Overridepublic void onCreateContextMenu(ContextMenu menu, View v, ContextMenuInfo menuInfo) {Log.i("MenuActivity","onCreateContextMenu");if(v.getId()==R.id.focus_text){SubMenu textMenu=menu.addSubMenu("Change Text");textMenu.add(0,ID_TEXT1,0,choices[0]);textMenu.add(0,ID_TEXT2,0,choices[1]);textMenu.add(0,ID_TEXT3,0,choices[2]);menu.add(0,ID_DEFAULT,0,"Original Text");}super.onCreateContextMenu(menu, v, menuInfo);}@Overridepublic boolean onCreateOptionsMenu(Menu menu) {Log.i("MenuActivity","onCreateOptionsMenu");menu.add(GROUP_DEFAULT, MENU_ADD, 0, "Add").setIcon(R.drawable.icon);menu.add(GROUP_DEFAULT,MENU_SEND,0,"Send");menu.add(GROUP_DEL,MENU_DEL,0,"Delete");return super.onCreateOptionsMenu(menu);}@Overridepublic boolean onOptionsItemSelected(MenuItem item) {switch(item.getItemId()){case MENU_ADD:createNote();break;case MENU_SEND:sendNote();break;case MENU_DEL:deleteNote();break;}return true;}@Overridepublic boolean onPrepareOptionsMenu(Menu menu) {Log.i("MenuActivity","onPrepareOptionsMenu");if(itemNum>0){menu.setGroupVisible(GROUP_DEL, true);}else{menu.setGroupVisible(GROUP_DEL, false);}return super.onPrepareOptionsMenu(menu);}@Overridepublic boolean onContextItemSelected(MenuItem item) {switch(item.getItemId()){case ID_DEFAULT:bv.setText("Hello");return true;case ID_TEXT1:case ID_TEXT2:case ID_TEXT3: bv.setText(choices[item.getItemId()-1]); return true;}return super.onContextItemSelected(item);}void createNote(){itemNum++;}void deleteNote(){itemNum--;}void sendNote(){Toast.makeText(this, "Item: "+itemNum,Toast.LENGTH_LONG).show();}} 总结调用顺序：
点击“Menu" 键时，调用 onCreateOptionsMenu---->onPrepareOptionsMenu.之后，再点击‘Menu" 键时，onCreateOptionsMenu不会被调用，但onPrepareOptionsMenu会被调用，在这里可以动态的改变菜单。
至于ContextMenu，每次长按view. 弹出菜单栏，都会调用onCreateContextMenu.
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