Intent intent = getIntent();
Intent intent2 = new Intent();
通常通过getIntent()方法获取到是非空的，即类似于：
intent：Intent { act=android.intent.action.MAIN cat=[android.intent.category.LAUNCHER] flg=0x10000000 cmp=com.example.menutest/.MainActivity }
intent2 是通过new 方式实例化的，肯定为null。
一般情况下我们需要用getIntent()方式来获取到本Activity的intent。
intent通常用于跳转,inent有个setAction()方法，官方文档的解释如下：
Set the general action to be performed.
- Parameters:
- action An action name, such as ACTION_VIEW. Application-specific actions should be prefixed with the vendor's package name.
- Returns:
- Returns the same Intent object, for chaining multiple calls into a single statement.
- See Also:
- getAction
- 实际上，设置action即，setAction(String action)这个方法通常是用来判断是点击了哪个按钮，然后来做相应的判断以及数据处理。
- 有如下场景，比如之前的那个记事本的应用实例里，
， - 如何判断是点了添加新日记还是检测呢，那么就可以在public boolean onOptionsItemSelected(MenuItem item) {}这个方法里进行判断，如果点了添加新日记，那么我们就给新建一个intent0,给这个intent0绑定一个action即绑定一个字符串，这个所谓的action实际上就是一个字符串。具体代码如下：
-
1 public boolean onOptionsItemSelected(MenuItem item) { 2 3 switch (item.getItemId()) { 4 case MENU_ITEM_INSERT: 5 6 Intent intent0 = new Intent(this, MyDiaryEdit.class); 7 //设置action，跳到第二个页面的时候就通过这个action来判断点了哪个按钮 8 intent0.setAction(MyDiaryEdit.INSERT_TEXT_ACTION); 9 System.out.println("intent0已经设置了Action，"); 10 /* 11 * getIntent():Return the intent that started this activity 12 * getIntent().getData(): Retrieve data this intent is operating on. 13 * Returns,The URI of the data this intent is targeting or null. 14 */ 15 intent0.setData(getIntent().getData());//intent设置URI 16 System.out.println("Return the intent that started this activity,the intent:"+getIntent()); 17 startActivity(intent0); 18 return true; 19 20 case MENU_ITEM_EDIT: 21 22 Intent intent1 = new Intent(this, MyDiaryEdit.class); 23 intent1.setAction(MyDiaryEdit.EDIT_TEXT_ACTION); 24 intent1.setData(item.getIntent().getData()); 25 startActivity(intent1); 26 return true; 27 28 case MENU_ITEM_DELETE: 29 Uri uri = ContentUris.withAppendedId(getIntent().getData(), 30 getListView().getSelectedItemId()); 31 getContentResolver().delete(uri, null, null); 32 rewindView(); 33 } 34 35 return super.onOptionsItemSelected(item); 36 }
第二个页面判断是点了哪个按钮的代码：
1 protected void onCreate(Bundle savedInstanceState) { 2 super.onCreate(savedInstanceState); 3 setTheme(android.R.style.Theme_Black); 4 //Return the intent that started this activity. 5 final Intent intent = getIntent(); 6 //获取intent里到底是绑定action字符串，下面用来判断是点了哪个按钮 7 final String action = intent.getAction(); 8 setContentView(R.layout.mydiaryedit);//添加对应的layout 9 System.out.println("intent.getAction():"+intent.getAction()); 10 myToast("intent.getAction():"+intent.getAction()); 11 TextView wyl_tv = (TextView) findViewById(R.id.wyl_txt); 12 wyl_tv.setText("intent.getAction():"+intent.getAction()+"; " 13 + " URI uri = intent.getData(): "+intent.getData()+"; MyDiaryEdit.java的intent："+getIntent()); 14 mTitleText = (EditText) findViewById(R.id.title); 15 mBodyText = (EditText) findViewById(R.id.body); 16 17 confirmButton = (Button) findViewById(R.id.confirm); 18 modifyButton = (Button) findViewById(R.id.modified); 19 20 if (EDIT_TEXT_ACTION.equals(action)) { 21 /* 22 * EDIT_TEXT_ACTION.equals(action),EDIT_TEXT_ACTION就是前一个 23 * 页面中intent.setAction的时候设置的哪个字符串，这样就能够判断是不是点了新增日记的按钮了 24 */ 25 mState = STATE_EDIT; 26 mTitleText.setEnabled(false);//设置为不可编辑 27 mBodyText.setEnabled(false);//设置不可编辑 28 modifyButton.setVisibility(View.VISIBLE); 29 mUri = intent.getData(); 30 mCursor = managedQuery(mUri, projection, null, null, null); 31 mCursor.moveToFirst(); 32 String title = mCursor.getString(1); 33 mTitleText.setTextKeepState(title); 34 String body = mCursor.getString(2); 35 mBodyText.setTextKeepState(body); 36 37 setResult(RESULT_OK, new Intent(MyDiaryEdit.EDIT_TEXT_ACTION, mUri)); 38 setTitle("编辑日记"); 39 } else if (INSERT_TEXT_ACTION.equals(action)) { 40 mState = STATE_INSERT; 41 setTitle("新建日记"); 42 } else { 43 44 Log.e(TAG, "no such action error"); 45 MyDiaryEdit.this.finish(); 46 47 return; 48 } 49 50 confirmButton.setOnClickListener(new MyBtnOnClickListen()); 51 modifyButton.setOnClickListener(new MyBtnOnClickListen()); 52 53 }