[PS:还是以GOOGLE原生的BluetoothChat为例]

1. startActivity与startActivityForResult的区别

startActivity( ) 仅仅是跳转到目标页面，若是想跳回当前页面，则必须再使用一次startActivity( )。

startActivityForResult( ) 可以一次性完成这项任务，当程序执行到这段代码的时候，假若从T1Activity跳转到下一个Text2Activity，

而当这个Text2Activity调用了finish()方法以后，程序会自动跳转回T1Activity，并调用前一个T1Activity中的onActivityResult( )方法。

例如在BluetoothChat类中，对跳转到DeviceListActivity类采用的是startActivityForResult( ) 方式：

　　@Override    public boolean onOptionsItemSelected(MenuItem item) {        Intent serverIntent = null;        switch (item.getItemId()) {        case R.id.secure_connect_scan:            // Launch the DeviceListActivity to see devices and do scan            serverIntent = new Intent(this, DeviceListActivity.class);            startActivityForResult(serverIntent, REQUEST_CONNECT_DEVICE_SECURE);            return true;        case R.id.insecure_connect_scan:            // Launch the DeviceListActivity to see devices and do scan            serverIntent = new Intent(this, DeviceListActivity.class);            startActivityForResult(serverIntent, REQUEST_CONNECT_DEVICE_INSECURE);            return true;        case R.id.discoverable:            // Ensure this device is discoverable by others            ensureDiscoverable();            return true;        }        return false;    }

在DeviceActivity中则使用setResult()方法返回值：

　　// The on-click listener for all devices in the ListViews    private OnItemClickListener mDeviceClickListener = new OnItemClickListener() {        public void onItemClick(AdapterView
         av, View v, int arg2, long arg3) {            // Cancel discovery because it's costly and we're about to connect            mBtAdapter.cancelDiscovery();            // Get the device MAC address, which is the last 17 chars in the View            String info = ((TextView) v).getText().toString();            String address = info.substring(info.length() - 17);            // Create the result Intent and include the MAC address            Intent intent = new Intent();            intent.putExtra(EXTRA_DEVICE_ADDRESS, address);            // Set result and finish this Activity            setResult(Activity.RESULT_OK, intent);            finish();        }    };

但是，要注意，如果在startActivityForResult跳转到的Activity里面设置setResult，结果并不会马上返回给parent的Activity，只有当前Activity被finish，

结果才会被发送给parent的onActivityResult去处理：

　　public void onActivityResult(int requestCode, int resultCode, Intent data) {        if(D) Log.d(TAG, "onActivityResult " + resultCode);        switch (requestCode) {        case REQUEST_CONNECT_DEVICE_SECURE:            // When DeviceListActivity returns with a device to connect            if (resultCode == Activity.RESULT_OK) {                connectDevice(data, true);            }            break;        case REQUEST_CONNECT_DEVICE_INSECURE:            // When DeviceListActivity returns with a device to connect            if (resultCode == Activity.RESULT_OK) {                connectDevice(data, false);            }            break;        case REQUEST_ENABLE_BT:            // When the request to enable Bluetooth returns            if (resultCode == Activity.RESULT_OK) {                // Bluetooth is now enabled, so set up a chat session                setupChat();            } else {                // User did not enable Bluetooth or an error occurred                Log.d(TAG, "BT not enabled");                Toast.makeText(this, R.string.bt_not_enabled_leaving, Toast.LENGTH_SHORT).show();                finish();            }        }    }

 2. setResult()的退出时机

这里的一个例子是提前调用setResult()设置好退出机制，以应对用户按"BACK"的情况：

　　@Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        // Setup the window        requestWindowFeature(Window.FEATURE_INDETERMINATE_PROGRESS);        setContentView(R.layout.device_list);        // Set result CANCELED in case the user backs out        setResult(Activity.RESULT_CANCELED);        // Initialize the button to perform device discovery        Button scanButton = (Button) findViewById(R.id.button_scan);        scanButton.setOnClickListener(new OnClickListener() {            public void onClick(View v) {                doDiscovery();                v.setVisibility(View.GONE);            }        });        // Initialize array adapters. One for already paired devices and        // one for newly discovered devices        mPairedDevicesArrayAdapter = new ArrayAdapter
        
         (this, R.layout.device_name);        mNewDevicesArrayAdapter = new ArrayAdapter
         
          (this, R.layout.device_name);        // Find and set up the ListView for paired devices        ListView pairedListView = (ListView) findViewById(R.id.paired_devices);        pairedListView.setAdapter(mPairedDevicesArrayAdapter);        pairedListView.setOnItemClickListener(mDeviceClickListener);        // Find and set up the ListView for newly discovered devices        ListView newDevicesListView = (ListView) findViewById(R.id.new_devices);        newDevicesListView.setAdapter(mNewDevicesArrayAdapter);        newDevicesListView.setOnItemClickListener(mDeviceClickListener);        // Register for broadcasts when a device is discovered        IntentFilter filter = new IntentFilter(BluetoothDevice.ACTION_FOUND);        this.registerReceiver(mReceiver, filter);        // Register for broadcasts when discovery has finished        filter = new IntentFilter(BluetoothAdapter.ACTION_DISCOVERY_FINISHED);        this.registerReceiver(mReceiver, filter);        // Get the local Bluetooth adapter        mBtAdapter = BluetoothAdapter.getDefaultAdapter();        // Get a set of currently paired devices        Set
          
            pairedDevices = mBtAdapter.getBondedDevices();        // If there are paired devices, add each one to the ArrayAdapter        if (pairedDevices.size() > 0) {            findViewById(R.id.title_paired_devices).setVisibility(View.VISIBLE);            for (BluetoothDevice device : pairedDevices) {                mPairedDevicesArrayAdapter.add(device.getName() + "\n" + device.getAddress());            }        } else {            String noDevices = getResources().getText(R.string.none_paired).toString();            mPairedDevicesArrayAdapter.add(noDevices);        }    }