<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools" android:layout_width="match_parent"
    android:layout_height="match_parent" android:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    tools:context="wifi.app.wei.com.myapplication.MainActivity">


    <RelativeLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:padding="10dp"
        >

        <ImageView
            android:id="@+id/image"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:src="@mipmap/eye_close"
            android:layout_alignParentRight="true"
            android:layout_centerVertical="true"
            />

        <EditText
            android:id="@+id/pass_et"
            android:layout_toLeftOf="@id/image"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:inputType="textPassword"
            />

    </RelativeLayout>


</RelativeLayout>

package wifi.app.wei.com.myapplication;

import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.text.InputType;
import android.view.View;
import android.widget.EditText;
import android.widget.ImageView;

public class MainActivity extends AppCompatActivity {

    private ImageView imageView ;
    private EditText editText ;
    boolean eyeOpen = false ;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main );
        imageView = (ImageView) findViewById( R.id.image) ;
        editText = (EditText) findViewById( R.id.pass_et);

        imageView.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                if ( eyeOpen ){
                    //密码 TYPE_CLASS_TEXT 和 TYPE_TEXT_VARIATION_PASSWORD 必须一起使用
                    editText.setInputType(InputType.TYPE_CLASS_TEXT | InputType.TYPE_TEXT_VARIATION_PASSWORD);
                    imageView.setImageResource( R.mipmap.eye_close );
                    eyeOpen = false ;
                }else {
                    //明文
                    editText.setInputType( InputType.TYPE_TEXT_VARIATION_VISIBLE_PASSWORD );
                    imageView.setImageResource( R.mipmap.eye_open );
                    eyeOpen = true ;
                }
            }
        });
    }
}

package wifi.app.wei.com.myapplication;

import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.text.method.HideReturnsTransformationMethod;
import android.text.method.PasswordTransformationMethod;
import android.view.View;
import android.widget.EditText;
import android.widget.ImageView;

public class MainActivity extends AppCompatActivity {

    private ImageView imageView ;
    private EditText editText ;
    boolean eyeOpen = false ;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main );
        imageView = (ImageView) findViewById( R.id.image) ;
        editText = (EditText) findViewById( R.id.pass_et);

        imageView.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                if ( eyeOpen ){
                    //密码
                    editText.setTransformationMethod(PasswordTransformationMethod.getInstance());
                    imageView.setImageResource( R.mipmap.eye_close );
                    eyeOpen = false ;
                }else {
                    //明文
                    editText.setTransformationMethod(HideReturnsTransformationMethod.getInstance());
                    imageView.setImageResource( R.mipmap.eye_open );
                    eyeOpen = true ;
                }
            }
        });
    }
}