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startActivity(Intent)/startActivityForResult(Intent)：来启动一个Activity
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显式Intent：通过组件名指定启动的目标组件,比如startActivity(new Intent(A.this,B.class)); 每次启动的组件只有一个
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隐式Intent:不指定组件名,而指定Intent的Action,Data,或Category,当我们启动组件时, 会去匹配AndroidManifest.xml相关组件的Intent-filter,逐一匹配出满足属性的组件,当不止一个满足时, 会弹出一个让我们选择启动哪个的对话框
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Intent参数问题: .class是获得这个类，类型是Class，this是这个类的实例，类型是这个类 只有Class.this和.class是同类型
- AlertDialog
package com.myapplication;
import android.content.DialogInterface;
import android.support.v7.app.AlertDialog;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.ImageView;
import android.widget.ProgressBar;
import android.widget.Toast;
public class MainActivity extends AppCompatActivity {
private EditText editText;
private ImageView imageView;
private ProgressBar progressBar;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Button button_1 = findViewById(R.id.button_1);
imageView = findViewById(R.id.pic);
editText = findViewById(R.id.edit);
progressBar = findViewById(R.id.bar);
button_1.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
switch (v.getId()) {
case R.id.button_1:
AlertDialog.Builder dialog;
dialog = new AlertDialog.Builder(MainActivity.this);
dialog.setTitle("这是一个提醒");
dialog.setMessage("你要删除么？");
dialog.setCancelable(false);
dialog.setPositiveButton("ok", new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialog, int which) {
Toast.makeText(MainActivity.this,"you click ok",Toast.LENGTH_SHORT).show();
}
});
dialog.setNegativeButton("cancle", new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialog, int which) {
Toast.makeText(MainActivity.this,"you click Cancle",Toast.LENGTH_SHORT).show();
}
});
dialog.show();
break;
default:
break;
}
}
});
}
}- ProgressDialog
package com.myapplication;
import android.app.ProgressDialog;
import android.content.DialogInterface;
import android.support.v7.app.AlertDialog;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.ImageView;
import android.widget.ProgressBar;
import android.widget.Toast;
public class MainActivity extends AppCompatActivity {
private EditText editText;
private ImageView imageView;
private ProgressBar progressBar;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Button button_1 = findViewById(R.id.button_1);
imageView = findViewById(R.id.pic);
editText = findViewById(R.id.edit);
progressBar = findViewById(R.id.bar);
button_1.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
switch (v.getId()) {
case R.id.button_1:
ProgressDialog progressDialog=new ProgressDialog(MainActivity.this);
progressDialog.setTitle("this is a progressdialog");
progressDialog.setMessage("Loading...");
progressDialog.setCancelable(true);;
progressDialog.show();
break;
default:
break;
}
}
});
}
}