Andriod 插件知识

package com.example.lovej.testapp;

import android.app.Activity;
import android.app.AlertDialog;
import android.app.ProgressDialog;
import android.content.DialogInterface;
import android.content.Intent;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.view.Window;
import android.widget.Button;
import android.widget.EditText;
import android.widget.ProgressBar;
import android.widget.TextView;
import android.widget.Toast;

/**
 * Created by lovej on 2016/7/25 0025.
 */
public class SecondActivity extends Activity {
    private TextView tvAt2;
    private EditText username;
    private EditText password;
    private ProgressBar progressBar;

    @Override
    protected void onCreate(Bundle saveInstanceState){
        super.onCreate(saveInstanceState);
        requestWindowFeature(Window.FEATURE_NO_TITLE);
        setContentView(R.layout.second_layout);
        Intent output = getIntent();
        Bundle data = output.getExtras();
        //定义textView
        tvAt2 = (TextView) findViewById(R.id.tv2);
        username =(EditText) findViewById(R.id.editText4);
        password =(EditText) findViewById(R.id.editText5);
        progressBar = (ProgressBar) findViewById(R.id.progressBar_1);
        //在tvAt2这个textview中使用getString 和 getInt 来获取字符串
        tvAt2.setText(String.format("Name: %s, Id: %d",data.getString("Name"),data.getInt("Id")));

        Button button2 = (Button) findViewById(R.id.button_2_2);
        Button button1 = (Button) findViewById(R.id.button_2_1);
        button2.setOnClickListener(new View.OnClickListener(){
            @Override
            public void onClick(View view){
                Intent intent = new Intent();
                String in = username.getText().toString();
                Toast.makeText(SecondActivity.this, in, Toast.LENGTH_SHORT).show();
                intent.putExtra("UN",username.getText().toString());
                intent.putExtra("PW",password.getText().toString());
                setResult(RESULT_OK,intent);
                //建立一个确认窗口来让用户确认信息
                AlertDialog.Builder dialog = new AlertDialog.Builder(SecondActivity.this);
                //确认信息的标题
                dialog.setTitle("Double check");
                //确认信息
                dialog.setMessage("Create your account???");
                //右边按钮
                dialog.setPositiveButton("Cancel", new DialogInterface.OnClickListener() {
                    @Override
                    public void onClick(DialogInterface dialogInterface, int i) {

                    }
                });
                //左边按钮
                dialog.setNegativeButton("OK", new DialogInterface.OnClickListener() {
                    @Override
                    public void onClick(DialogInterface dialogInterface, int i) {
                        finish();
                    }
                });
                dialog.show();

            }
        });

	//  进度条 显示2秒后消失。
        button1.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                final ProgressDialog pD = new ProgressDialog.(SecondActivity.this);
                pD.setTitle("This is a progress dialog");
                pD.setMessage("Connecting to the server(disappear in 2 sec)");
                pD.show();
                Thread thread = new Thread(){
                    public void run(){
                        try{
                            sleep(2000);
                        }catch (Exception e){
                            e.printStackTrace();
                        }
                        pD.dismiss();
                    }
                };
                thread.start();
               pD.setCancelable(true);
               

            }
        });

        Button button3 = (Button) findViewById(R.id.button_2_3);
        button3.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                //如果progressbar 不可见的话就显示progressbarBar ，否则隐藏progressbar
                if(progressBar.getVisibility()==View.GONE){
                    progressBar.setVisibility(View.VISIBLE);
                }else{
                    progressBar.setVisibility(View.GONE);
                }
            }
        });
    }
    //返回键
    @Override
    public void onBackPressed(){
        Intent intent = new Intent();
        //把log up canceled信息传递给data_return这个key
        intent.putExtra("data_return","sign up canceled");
        setResult(RESULT_CANCELED,intent);
        finish();
    }
}

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显示Intent使用new Intent(MainActivity.this, SecondActivity.class);来启动activity；
隐式intent使用new Intent("aa")；来启动activity，起作用是可以在不同的app中调用此acitivity。如果想不允许在其他app中调用这个app的话，在manifest注册文件activity中
<activity android:name=".ThirdActivity" android:exported="false" >就会阻止别的app启动该acitivity。